Triangle calculator SSA

Please enter two sides and a non-included angle
°


Triangle has two solutions with side c=806.783292577 and with side c=379.6454871274

#1 Acute scalene triangle.

Sides: a = 890   b = 697   c = 806.783292577

Area: T = 267639.6022111
Perimeter: p = 2393.783292577
Semiperimeter: s = 1196.891146289

Angle ∠ A = α = 72.15768784201° = 72°9'25″ = 1.25993751064 rad
Angle ∠ B = β = 48.2° = 48°12' = 0.84112486995 rad
Angle ∠ C = γ = 59.64331215799° = 59°38'35″ = 1.04109688477 rad

Height: ha = 601.4377308115
Height: hb = 767.9765902759
Height: hc = 663.4743639718

Median: ma = 608.5476501639
Median: mb = 774.6277068115
Median: mc = 690.094407161

Inradius: r = 223.6122257595
Circumradius: R = 467.4876545708

Vertex coordinates: A[806.783292577; 0] B[0; 0] C[593.2143898522; 663.4743639718]
Centroid: CG[466.6665608097; 221.1587879906]
Coordinates of the circumscribed circle: U[403.3911462885; 236.2660445461]
Coordinates of the inscribed circle: I[499.8911462885; 223.6122257595]

Exterior (or external, outer) angles of the triangle:
∠ A' = α' = 107.843312158° = 107°50'35″ = 1.25993751064 rad
∠ B' = β' = 131.8° = 131°48' = 0.84112486995 rad
∠ C' = γ' = 120.357687842° = 120°21'25″ = 1.04109688477 rad


How did we calculate this triangle?

The calculation of the triangle progress in two phases. The first phase is such that we try to calculate all three sides of the triangle from the input parameters. The first phase is different for the different triangles query entered. The second phase is the calculation of other characteristics of the triangle, such as angles, area, perimeter, heights, the center of gravity, circle radii, etc. Some input data also results in two to three correct triangle solutions (e.g., if the specified triangle area and two sides - typically resulting in both acute and obtuse) triangle).

1. Use the Law of Cosines

a=890 b=697 β=4812  b2=a2+c22accosβ 6972=8902+c22 890 c cos(4812)  c21186.428c+306291=0  p=1;q=1186.428;r=306291 D=q24pr=1186.428241306291=182446.917599 D>0  c1,2=q±D2p=1186.43±182446.922 c1,2=593.21389852±213.569027248 c1=806.78292577 c2=379.644871274   Factored form of the equation:  (c806.78292577)(c379.644871274)=0  c>0a = 890 \ \\ b = 697 \ \\ β = 48^\circ 12' \ \\ \ \\ b^2 = a^2 + c^2 - 2ac \cos β \ \\ 697^2 = 890^2 + c^2 -2 \cdot \ 890 \cdot \ c \cdot \ \cos (48^\circ 12') \ \\ \ \\ c^2 -1186.428c +306291 =0 \ \\ \ \\ p=1; q=-1186.428; r=306291 \ \\ D = q^2 - 4pr = 1186.428^2 - 4\cdot 1 \cdot 306291 = 182446.917599 \ \\ D>0 \ \\ \ \\ c_{1,2} = \dfrac{ -q \pm \sqrt{ D } }{ 2p } = \dfrac{ 1186.43 \pm \sqrt{ 182446.92 } }{ 2 } \ \\ c_{1,2} = 593.21389852 \pm 213.569027248 \ \\ c_{1} = 806.78292577 \ \\ c_{2} = 379.644871274 \ \\ \ \\ \text{ Factored form of the equation: } \ \\ (c -806.78292577) (c -379.644871274) = 0 \ \\ \ \\ c>0

Now we know the lengths of all three sides of the triangle, and the triangle is uniquely determined. Next, we calculate another its characteristics - same procedure as calculation of the triangle from the known three sides SSS.

a=890 b=697 c=806.78a = 890 \ \\ b = 697 \ \\ c = 806.78

2. The triangle perimeter is the sum of the lengths of its three sides

p=a+b+c=890+697+806.78=2393.78p = a+b+c = 890+697+806.78 = 2393.78

3. Semiperimeter of the triangle

The semiperimeter of the triangle is half its perimeter. The semiperimeter frequently appears in formulas for triangles that it is given a separate name. By the triangle inequality, the longest side length of a triangle is less than the semiperimeter.

s=p2=2393.782=1196.89s = \dfrac{ p }{ 2 } = \dfrac{ 2393.78 }{ 2 } = 1196.89

4. The triangle area using Heron's formula

Heron's formula gives the area of a triangle when the length of all three sides are known. There is no need to calculate angles or other distances in the triangle first. Heron's formula works equally well in all cases and types of triangles.

T=s(sa)(sb)(sc) T=1196.89(1196.89890)(1196.89697)(1196.89806.78) T=71630956618.4=267639.6T = \sqrt{ s(s-a)(s-b)(s-c) } \ \\ T = \sqrt{ 1196.89(1196.89-890)(1196.89-697)(1196.89-806.78) } \ \\ T = \sqrt{ 71630956618.4 } = 267639.6

5. Calculate the heights of the triangle from its area.

There are many ways to find the height of the triangle. The easiest way is from the area and base length. The area of a triangle is half of the product of the length of the base and the height. Every side of the triangle can be a base; there are three bases and three heights (altitudes). Triangle height is the perpendicular line segment from a vertex to a line containing the base.

T=aha2  ha=2 Ta=2 267639.6890=601.44 hb=2 Tb=2 267639.6697=767.98 hc=2 Tc=2 267639.6806.78=663.47T = \dfrac{ a h _a }{ 2 } \ \\ \ \\ h _a = \dfrac{ 2 \ T }{ a } = \dfrac{ 2 \cdot \ 267639.6 }{ 890 } = 601.44 \ \\ h _b = \dfrac{ 2 \ T }{ b } = \dfrac{ 2 \cdot \ 267639.6 }{ 697 } = 767.98 \ \\ h _c = \dfrac{ 2 \ T }{ c } = \dfrac{ 2 \cdot \ 267639.6 }{ 806.78 } = 663.47

6. Calculation of the inner angles of the triangle using a Law of Cosines

The Law of Cosines is useful for finding the angles of a triangle when we know all three sides. The cosine rule, also known as the law of cosines, relates all three sides of a triangle with an angle of a triangle. The Law of Cosines is the extrapolation of the Pythagorean theorem for any triangle. Pythagorean theorem works only in a right triangle. Pythagorean theorem is a special case of the Law of Cosines and can be derived from it because the cosine of 90° is 0. It is best to find the angle opposite the longest side first. With the Law of Cosines, there is also no problem with obtuse angles as with the Law of Sines, because cosine function is negative for obtuse angles, zero for right, and positive for acute angles. We also use inverse cosine called arccosine to determine the angle from cosine value.

a2=b2+c22bccosα  α=arccos(b2+c2a22bc)=arccos(6972+806.78289022 697 806.78)=72925"  b2=a2+c22accosβ β=arccos(a2+c2b22ac)=arccos(8902+806.78269722 890 806.78)=4812 γ=180αβ=18072925"4812=593835"a^2 = b^2+c^2 - 2bc \cos α \ \\ \ \\ α = \arccos(\dfrac{ b^2+c^2-a^2 }{ 2bc } ) = \arccos(\dfrac{ 697^2+806.78^2-890^2 }{ 2 \cdot \ 697 \cdot \ 806.78 } ) = 72^\circ 9'25" \ \\ \ \\ b^2 = a^2+c^2 - 2ac \cos β \ \\ β = \arccos(\dfrac{ a^2+c^2-b^2 }{ 2ac } ) = \arccos(\dfrac{ 890^2+806.78^2-697^2 }{ 2 \cdot \ 890 \cdot \ 806.78 } ) = 48^\circ 12' \ \\ γ = 180^\circ - α - β = 180^\circ - 72^\circ 9'25" - 48^\circ 12' = 59^\circ 38'35"

7. Inradius

An incircle of a triangle is a circle which is tangent to each side. An incircle center is called incenter and has a radius named inradius. All triangles have an incenter, and it always lies inside the triangle. The incenter is the intersection of the three angle bisectors. The product of the inradius and semiperimeter (half the perimeter) of a triangle is its area.

T=rs r=Ts=267639.61196.89=223.61T = rs \ \\ r = \dfrac{ T }{ s } = \dfrac{ 267639.6 }{ 1196.89 } = 223.61

8. Circumradius

The circumcircle of a triangle is a circle that passes through all of the triangle's vertices, and the circumradius of a triangle is the radius of the triangle's circumcircle. Circumcenter (center of circumcircle) is the point where the perpendicular bisectors of a triangle intersect.

R=abc4 rs=890 697 806.784 223.612 1196.891=467.49R = \dfrac{ a b c }{ 4 \ r s } = \dfrac{ 890 \cdot \ 697 \cdot \ 806.78 }{ 4 \cdot \ 223.612 \cdot \ 1196.891 } = 467.49

9. Calculation of medians

A median of a triangle is a line segment joining a vertex to the midpoint of the opposite side. Every triangle has three medians, and they all intersect each other at the triangle's centroid. The centroid divides each median into parts in the ratio 2:1, with the centroid being twice as close to the midpoint of a side as it is to the opposite vertex. We use Apollonius's theorem to calculate the length of a median from the lengths of its side.

ma=2b2+2c2a22=2 6972+2 806.78289022=608.547 mb=2c2+2a2b22=2 806.782+2 890269722=774.627 mc=2a2+2b2c22=2 8902+2 6972806.7822=690.094m_a = \dfrac{ \sqrt{ 2b^2+2c^2 - a^2 } }{ 2 } = \dfrac{ \sqrt{ 2 \cdot \ 697^2+2 \cdot \ 806.78^2 - 890^2 } }{ 2 } = 608.547 \ \\ m_b = \dfrac{ \sqrt{ 2c^2+2a^2 - b^2 } }{ 2 } = \dfrac{ \sqrt{ 2 \cdot \ 806.78^2+2 \cdot \ 890^2 - 697^2 } }{ 2 } = 774.627 \ \\ m_c = \dfrac{ \sqrt{ 2a^2+2b^2 - c^2 } }{ 2 } = \dfrac{ \sqrt{ 2 \cdot \ 890^2+2 \cdot \ 697^2 - 806.78^2 } }{ 2 } = 690.094



#2 Obtuse scalene triangle.

Sides: a = 890   b = 697   c = 379.6454871274

Area: T = 125942.1822272
Perimeter: p = 1966.645487127
Semiperimeter: s = 983.3222435637

Angle ∠ A = α = 107.843312158° = 107°50'35″ = 1.88222175472 rad
Angle ∠ B = β = 48.2° = 48°12' = 0.84112486995 rad
Angle ∠ C = γ = 23.95768784201° = 23°57'25″ = 0.41881264069 rad

Height: ha = 283.0166139937
Height: hb = 361.384359332
Height: hc = 663.4743639718

Median: ma = 341.9721656928
Median: mb = 588.7810828613
Median: mc = 776.4880484577

Inradius: r = 128.0788214945
Circumradius: R = 467.4876545708

Vertex coordinates: A[379.6454871274; 0] B[0; 0] C[593.2143898522; 663.4743639718]
Centroid: CG[324.2866256599; 221.1587879906]
Coordinates of the circumscribed circle: U[189.8222435637; 427.2133194257]
Coordinates of the inscribed circle: I[286.3222435637; 128.0788214945]

Exterior (or external, outer) angles of the triangle:
∠ A' = α' = 72.15768784201° = 72°9'25″ = 1.88222175472 rad
∠ B' = β' = 131.8° = 131°48' = 0.84112486995 rad
∠ C' = γ' = 156.043312158° = 156°2'35″ = 0.41881264069 rad

Calculate another triangle

How did we calculate this triangle?

The calculation of the triangle progress in two phases. The first phase is such that we try to calculate all three sides of the triangle from the input parameters. The first phase is different for the different triangles query entered. The second phase is the calculation of other characteristics of the triangle, such as angles, area, perimeter, heights, the center of gravity, circle radii, etc. Some input data also results in two to three correct triangle solutions (e.g., if the specified triangle area and two sides - typically resulting in both acute and obtuse) triangle).

1. Use the Law of Cosines

a=890 b=697 β=4812  b2=a2+c22accosβ 6972=8902+c22 890 c cos(4812)  c21186.428c+306291=0  p=1;q=1186.428;r=306291 D=q24pr=1186.428241306291=182446.917599 D>0  c1,2=q±D2p=1186.43±182446.922 c1,2=593.21389852±213.569027248 c1=806.78292577 c2=379.644871274   Factored form of the equation:  (c806.78292577)(c379.644871274)=0  c>0a = 890 \ \\ b = 697 \ \\ β = 48^\circ 12' \ \\ \ \\ b^2 = a^2 + c^2 - 2ac \cos β \ \\ 697^2 = 890^2 + c^2 -2 \cdot \ 890 \cdot \ c \cdot \ \cos (48^\circ 12') \ \\ \ \\ c^2 -1186.428c +306291 =0 \ \\ \ \\ p=1; q=-1186.428; r=306291 \ \\ D = q^2 - 4pr = 1186.428^2 - 4\cdot 1 \cdot 306291 = 182446.917599 \ \\ D>0 \ \\ \ \\ c_{1,2} = \dfrac{ -q \pm \sqrt{ D } }{ 2p } = \dfrac{ 1186.43 \pm \sqrt{ 182446.92 } }{ 2 } \ \\ c_{1,2} = 593.21389852 \pm 213.569027248 \ \\ c_{1} = 806.78292577 \ \\ c_{2} = 379.644871274 \ \\ \ \\ \text{ Factored form of the equation: } \ \\ (c -806.78292577) (c -379.644871274) = 0 \ \\ \ \\ c>0

Now we know the lengths of all three sides of the triangle, and the triangle is uniquely determined. Next, we calculate another its characteristics - same procedure as calculation of the triangle from the known three sides SSS.

a=890 b=697 c=379.64a = 890 \ \\ b = 697 \ \\ c = 379.64

2. The triangle perimeter is the sum of the lengths of its three sides

p=a+b+c=890+697+379.64=1966.64p = a+b+c = 890+697+379.64 = 1966.64

3. Semiperimeter of the triangle

The semiperimeter of the triangle is half its perimeter. The semiperimeter frequently appears in formulas for triangles that it is given a separate name. By the triangle inequality, the longest side length of a triangle is less than the semiperimeter.

s=p2=1966.642=983.32s = \dfrac{ p }{ 2 } = \dfrac{ 1966.64 }{ 2 } = 983.32

4. The triangle area using Heron's formula

Heron's formula gives the area of a triangle when the length of all three sides are known. There is no need to calculate angles or other distances in the triangle first. Heron's formula works equally well in all cases and types of triangles.

T=s(sa)(sb)(sc) T=983.32(983.32890)(983.32697)(983.32379.64) T=15861433275.5=125942.18T = \sqrt{ s(s-a)(s-b)(s-c) } \ \\ T = \sqrt{ 983.32(983.32-890)(983.32-697)(983.32-379.64) } \ \\ T = \sqrt{ 15861433275.5 } = 125942.18

5. Calculate the heights of the triangle from its area.

There are many ways to find the height of the triangle. The easiest way is from the area and base length. The area of a triangle is half of the product of the length of the base and the height. Every side of the triangle can be a base; there are three bases and three heights (altitudes). Triangle height is the perpendicular line segment from a vertex to a line containing the base.

T=aha2  ha=2 Ta=2 125942.18890=283.02 hb=2 Tb=2 125942.18697=361.38 hc=2 Tc=2 125942.18379.64=663.47T = \dfrac{ a h _a }{ 2 } \ \\ \ \\ h _a = \dfrac{ 2 \ T }{ a } = \dfrac{ 2 \cdot \ 125942.18 }{ 890 } = 283.02 \ \\ h _b = \dfrac{ 2 \ T }{ b } = \dfrac{ 2 \cdot \ 125942.18 }{ 697 } = 361.38 \ \\ h _c = \dfrac{ 2 \ T }{ c } = \dfrac{ 2 \cdot \ 125942.18 }{ 379.64 } = 663.47

6. Calculation of the inner angles of the triangle using a Law of Cosines

The Law of Cosines is useful for finding the angles of a triangle when we know all three sides. The cosine rule, also known as the law of cosines, relates all three sides of a triangle with an angle of a triangle. The Law of Cosines is the extrapolation of the Pythagorean theorem for any triangle. Pythagorean theorem works only in a right triangle. Pythagorean theorem is a special case of the Law of Cosines and can be derived from it because the cosine of 90° is 0. It is best to find the angle opposite the longest side first. With the Law of Cosines, there is also no problem with obtuse angles as with the Law of Sines, because cosine function is negative for obtuse angles, zero for right, and positive for acute angles. We also use inverse cosine called arccosine to determine the angle from cosine value.

a2=b2+c22bccosα  α=arccos(b2+c2a22bc)=arccos(6972+379.64289022 697 379.64)=1075035"  b2=a2+c22accosβ β=arccos(a2+c2b22ac)=arccos(8902+379.64269722 890 379.64)=4812 γ=180αβ=1801075035"4812=235725"a^2 = b^2+c^2 - 2bc \cos α \ \\ \ \\ α = \arccos(\dfrac{ b^2+c^2-a^2 }{ 2bc } ) = \arccos(\dfrac{ 697^2+379.64^2-890^2 }{ 2 \cdot \ 697 \cdot \ 379.64 } ) = 107^\circ 50'35" \ \\ \ \\ b^2 = a^2+c^2 - 2ac \cos β \ \\ β = \arccos(\dfrac{ a^2+c^2-b^2 }{ 2ac } ) = \arccos(\dfrac{ 890^2+379.64^2-697^2 }{ 2 \cdot \ 890 \cdot \ 379.64 } ) = 48^\circ 12' \ \\ γ = 180^\circ - α - β = 180^\circ - 107^\circ 50'35" - 48^\circ 12' = 23^\circ 57'25"

7. Inradius

An incircle of a triangle is a circle which is tangent to each side. An incircle center is called incenter and has a radius named inradius. All triangles have an incenter, and it always lies inside the triangle. The incenter is the intersection of the three angle bisectors. The product of the inradius and semiperimeter (half the perimeter) of a triangle is its area.

T=rs r=Ts=125942.18983.32=128.08T = rs \ \\ r = \dfrac{ T }{ s } = \dfrac{ 125942.18 }{ 983.32 } = 128.08

8. Circumradius

The circumcircle of a triangle is a circle that passes through all of the triangle's vertices, and the circumradius of a triangle is the radius of the triangle's circumcircle. Circumcenter (center of circumcircle) is the point where the perpendicular bisectors of a triangle intersect.

R=abc4 rs=890 697 379.644 128.078 983.322=467.49R = \dfrac{ a b c }{ 4 \ r s } = \dfrac{ 890 \cdot \ 697 \cdot \ 379.64 }{ 4 \cdot \ 128.078 \cdot \ 983.322 } = 467.49

9. Calculation of medians

A median of a triangle is a line segment joining a vertex to the midpoint of the opposite side. Every triangle has three medians, and they all intersect each other at the triangle's centroid. The centroid divides each median into parts in the ratio 2:1, with the centroid being twice as close to the midpoint of a side as it is to the opposite vertex. We use Apollonius's theorem to calculate the length of a median from the lengths of its side.

ma=2b2+2c2a22=2 6972+2 379.64289022=341.972 mb=2c2+2a2b22=2 379.642+2 890269722=588.781 mc=2a2+2b2c22=2 8902+2 6972379.6422=776.48m_a = \dfrac{ \sqrt{ 2b^2+2c^2 - a^2 } }{ 2 } = \dfrac{ \sqrt{ 2 \cdot \ 697^2+2 \cdot \ 379.64^2 - 890^2 } }{ 2 } = 341.972 \ \\ m_b = \dfrac{ \sqrt{ 2c^2+2a^2 - b^2 } }{ 2 } = \dfrac{ \sqrt{ 2 \cdot \ 379.64^2+2 \cdot \ 890^2 - 697^2 } }{ 2 } = 588.781 \ \\ m_c = \dfrac{ \sqrt{ 2a^2+2b^2 - c^2 } }{ 2 } = \dfrac{ \sqrt{ 2 \cdot \ 890^2+2 \cdot \ 697^2 - 379.64^2 } }{ 2 } = 776.48

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