Triangle calculator SSA

Please enter two sides and a non-included angle
°


Triangle has two solutions with side c=105.34441726061 and with side c=71.43325226905

#1 Acute scalene triangle.

Sides: a = 125   b = 90   c = 105.34441726061

Area: T = 4655.59986755176
Perimeter: p = 320.34441726061
Semiperimeter: s = 160.17220863031

Angle ∠ A = α = 79.1410688732° = 79°8'26″ = 1.38112655907 rad
Angle ∠ B = β = 45° = 0.78553981634 rad
Angle ∠ C = γ = 55.8599311268° = 55°51'34″ = 0.97549288995 rad

Height: ha = 74.49895788083
Height: hb = 103.45877483448
Height: hc = 88.38883476483

Median: ma = 75.4488309133
Median: mb = 106.47215800157
Median: mc = 95.33217959785

Inradius: r = 29.06662298467
Circumradius: R = 63.64396103068

Vertex coordinates: A[105.34441726061; 0] B[0; 0] C[88.38883476483; 88.38883476483]
Centroid: CG[64.57875067515; 29.46327825494]
Coordinates of the circumscribed circle: U[52.67220863031; 35.71662613453]
Coordinates of the inscribed circle: I[70.17220863031; 29.06662298467]

Exterior (or external, outer) angles of the triangle:
∠ A' = α' = 100.8599311268° = 100°51'34″ = 1.38112655907 rad
∠ B' = β' = 135° = 0.78553981634 rad
∠ C' = γ' = 124.1410688732° = 124°8'26″ = 0.97549288995 rad

How did we calculate this triangle?

The calculation of the triangle has two phases. The first phase calculates all three sides of the triangle from the input parameters. The first phase is different for the different triangles query entered. The second phase calculates other triangle characteristics, 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=125 b=90 β=45°  b2=a2+c22accosβ 902=1252+c22 125 c cos45°  c2176.777c+7525=0  p=1;q=176.777;r=7525 D=q24pr=176.7772417525=1150 D>0  c1,2=2pq±D=2176.78±1150 c1,2=88.388348±16.955825 c1=105.344172606 c2=71.432522691   c>0  c=105.34

We know the lengths of all three sides of the triangle, so the triangle is uniquely specified. Next, we calculate another of its characteristics - the same procedure for calculating the triangle from the known three sides SSS.
a=125 b=90 c=105.34

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

p=a+b+c=125+90+105.34=320.34

3. Semiperimeter of the triangle

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

s=2p=2320.34=160.17

4. The triangle area using Heron's formula

Heron's formula gives the area of a triangle when the length of all three sides is 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=160.17(160.17125)(160.1790)(160.17105.34) T=21674599.03=4655.6

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 triangle area is half of the product of the base's length and 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=2aha  ha=a2 T=1252 4655.6=74.49 hb=b2 T=902 4655.6=103.46 hc=c2 T=105.342 4655.6=88.39

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

The Law of Cosines is useful for finding a triangle's angles 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 extrapolates 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 the cosine function is negative for obtuse angles, zero for right, and positive for acute angles. We also use an inverse cosine called arccosine to determine the angle from the cosine value.

a2=b2+c22bccosα  α=arccos(2bcb2+c2a2)=arccos(2 90 105.34902+105.3421252)=79°826"  b2=a2+c22accosβ β=arccos(2aca2+c2b2)=arccos(2 125 105.341252+105.342902)=45° γ=180°αβ=180°79°826"45°=55°5134"

7. Inradius

An incircle of a triangle is a tangent circle to each side. An incircle center is called an 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 a triangle's inradius and semiperimeter (half the perimeter) is its area.

T=rs r=sT=160.174655.6=29.07

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. The circumcenter (center of the circumcircle) is the point where the perpendicular bisectors of a triangle intersect.

R=4 rsabc=4 29.066 160.172125 90 105.34=63.64

9. Calculation of medians

A median of a triangle is a line segment joining a vertex to the opposite side's midpoint. 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 of 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 a median's length from its side's lengths.

ma=22b2+2c2a2=22 902+2 105.3421252=75.448 mb=22c2+2a2b2=22 105.342+2 1252902=106.472 mc=22a2+2b2c2=22 1252+2 902105.342=95.332


#2 Obtuse scalene triangle.

Sides: a = 125   b = 90   c = 71.43325226905

Area: T = 3156.90113244824
Perimeter: p = 286.43325226905
Semiperimeter: s = 143.21662613453

Angle ∠ A = α = 100.8599311268° = 100°51'34″ = 1.76603270629 rad
Angle ∠ B = β = 45° = 0.78553981634 rad
Angle ∠ C = γ = 34.1410688732° = 34°8'26″ = 0.59658674273 rad

Height: ha = 50.51104211917
Height: hb = 70.15333627663
Height: hc = 88.38883476483

Median: ma = 51.91438964918
Median: mb = 91.31770446793
Median: mc = 102.89224131096

Inradius: r = 22.0432897188
Circumradius: R = 63.64396103068

Vertex coordinates: A[71.43325226905; 0] B[0; 0] C[88.38883476483; 88.38883476483]
Centroid: CG[53.27436234463; 29.46327825494]
Coordinates of the circumscribed circle: U[35.71662613453; 52.67220863031]
Coordinates of the inscribed circle: I[53.21662613453; 22.0432897188]

Exterior (or external, outer) angles of the triangle:
∠ A' = α' = 79.1410688732° = 79°8'26″ = 1.76603270629 rad
∠ B' = β' = 135° = 0.78553981634 rad
∠ C' = γ' = 145.8599311268° = 145°51'34″ = 0.59658674273 rad

Calculate another triangle

How did we calculate this triangle?

The calculation of the triangle has two phases. The first phase calculates all three sides of the triangle from the input parameters. The first phase is different for the different triangles query entered. The second phase calculates other triangle characteristics, 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=125 b=90 β=45°  b2=a2+c22accosβ 902=1252+c22 125 c cos45°  c2176.777c+7525=0  p=1;q=176.777;r=7525 D=q24pr=176.7772417525=1150 D>0  c1,2=2pq±D=2176.78±1150 c1,2=88.388348±16.955825 c1=105.344172606 c2=71.432522691   c>0  c=105.34

We know the lengths of all three sides of the triangle, so the triangle is uniquely specified. Next, we calculate another of its characteristics - the same procedure for calculating the triangle from the known three sides SSS.
a=125 b=90 c=71.43

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

p=a+b+c=125+90+71.43=286.43

3. Semiperimeter of the triangle

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

s=2p=2286.43=143.22

4. The triangle area using Heron's formula

Heron's formula gives the area of a triangle when the length of all three sides is 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=143.22(143.22125)(143.2290)(143.2271.43) T=9966025.97=3156.9

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 triangle area is half of the product of the base's length and 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=2aha  ha=a2 T=1252 3156.9=50.51 hb=b2 T=902 3156.9=70.15 hc=c2 T=71.432 3156.9=88.39

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

The Law of Cosines is useful for finding a triangle's angles 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 extrapolates 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 the cosine function is negative for obtuse angles, zero for right, and positive for acute angles. We also use an inverse cosine called arccosine to determine the angle from the cosine value.

a2=b2+c22bccosα  α=arccos(2bcb2+c2a2)=arccos(2 90 71.43902+71.4321252)=100°5134"  b2=a2+c22accosβ β=arccos(2aca2+c2b2)=arccos(2 125 71.431252+71.432902)=45° γ=180°αβ=180°100°5134"45°=34°826"

7. Inradius

An incircle of a triangle is a tangent circle to each side. An incircle center is called an 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 a triangle's inradius and semiperimeter (half the perimeter) is its area.

T=rs r=sT=143.223156.9=22.04

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. The circumcenter (center of the circumcircle) is the point where the perpendicular bisectors of a triangle intersect.

R=4 rsabc=4 22.043 143.216125 90 71.43=63.64

9. Calculation of medians

A median of a triangle is a line segment joining a vertex to the opposite side's midpoint. 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 of 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 a median's length from its side's lengths.

ma=22b2+2c2a2=22 902+2 71.4321252=51.914 mb=22c2+2a2b2=22 71.432+2 1252902=91.317 mc=22a2+2b2c2=22 1252+2 90271.432=102.892

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