Triangle calculator

Please enter what you know about the triangle:
Symbols definition of ABC triangle

You have entered side a, b and angle γ.

Obtuse scalene triangle.

Sides: a = 0.03   b = 0.33   c = 0.312156509

Area: T = 0.004379192
Perimeter: p = 0.672156509
Semiperimeter: s = 0.3365782545

Angle ∠ A = α = 4.23300320762° = 4°13'48″ = 0.07438279872 rad
Angle ∠ B = β = 125.77699679238° = 125°46'12″ = 2.19551000404 rad
Angle ∠ C = γ = 50° = 0.8732664626 rad

Height: ha = 0.25327946662
Height: hb = 0.02329813333
Height: hc = 0.02443411095

Median: ma = 0.32105641943
Median: mb = 0.14875174656
Median: mc = 0.17550194237

Inradius: r = 0.01112927847
Circumradius: R = 0.20333596698

Vertex coordinates: A[0.312156509; 0] B[0; 0] C[-0.01875359741; 0.02443411095]
Centroid: CG[0.09880097053; 0.00881137032]
Coordinates of the circumscribed circle: U[0.1565782545; 0.13107170761]
Coordinates of the inscribed circle: I[0.0065782545; 0.01112927847]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 175.77699679238° = 175°46'12″ = 0.07438279872 rad
∠ B' = β' = 54.23300320762° = 54°13'48″ = 2.19551000404 rad
∠ C' = γ' = 130° = 0.8732664626 rad

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How did we calculate this triangle?

1. Input data entered: side a, b and angle γ.

a = 0.03 ; ; b = 0.33 ; ; gamma = 50° ; ;

2. Calculation of the third side c of the triangle using a Law of Cosines

c**2 = a**2+b**2 - 2ab cos gamma ; ; c = sqrt{ a**2+b**2 - 2ab cos gamma } ; ; c = sqrt{ 0.03**2+0.33**2 - 2 * 0.03 * 0.33 * cos(50° ) } ; ; c = 0.31 ; ;


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 = 0.03 ; ; b = 0.33 ; ; c = 0.31 ; ;

3. The triangle circumference is the sum of the lengths of its three sides

p = a+b+c = 0.03+0.33+0.31 = 0.67 ; ;

4. Semiperimeter of the triangle

s = fraction{ o }{ 2 } = fraction{ 0.67 }{ 2 } = 0.34 ; ;

5. The triangle area using Heron's formula

T = sqrt{ s(s-a)(s-b)(s-c) } ; ; T = sqrt{ 0.34 * (0.34-0.03)(0.34-0.33)(0.34-0.31) } ; ; T = sqrt{ 0 } = 0 ; ;

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

T = fraction{ a h _a }{ 2 } ; ; h _a = fraction{ 2 T }{ a } = fraction{ 2 * 0 }{ 0.03 } = 0.25 ; ; h _b = fraction{ 2 T }{ b } = fraction{ 2 * 0 }{ 0.33 } = 0.02 ; ; h _c = fraction{ 2 T }{ c } = fraction{ 2 * 0 }{ 0.31 } = 0.02 ; ;

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

a**2 = b**2+c**2 - 2bc cos( alpha ) ; ; alpha = arccos( fraction{ b**2+c**2-a**2 }{ 2bc } ) = arccos( fraction{ 0.33**2+0.31**2-0.03**2 }{ 2 * 0.33 * 0.31 } ) = 4° 13'48" ; ; beta = arccos( fraction{ a**2+c**2-b**2 }{ 2ac } ) = arccos( fraction{ 0.03**2+0.31**2-0.33**2 }{ 2 * 0.03 * 0.31 } ) = 125° 46'12" ; ; gamma = 180° - alpha - beta = 180° - 4° 13'48" - 125° 46'12" = 50° ; ;

8. Inradius

T = rs ; ; r = fraction{ T }{ s } = fraction{ 0 }{ 0.34 } = 0.01 ; ;

9. Circumradius

R = fraction{ a }{ 2 * sin( alpha ) } = fraction{ 0.03 }{ 2 * sin 4° 13'48" } = 0.2 ; ;

10. Calculation of medians

m_a = fraction{ sqrt{ 2 b**2+2c**2 - a**2 } }{ 2 } = fraction{ sqrt{ 2 * 0.33**2+2 * 0.31**2 - 0.03**2 } }{ 2 } = 0.321 ; ; m_b = fraction{ sqrt{ 2 c**2+2a**2 - b**2 } }{ 2 } = fraction{ sqrt{ 2 * 0.31**2+2 * 0.03**2 - 0.33**2 } }{ 2 } = 0.148 ; ; m_c = fraction{ sqrt{ 2 b**2+2a**2 - c**2 } }{ 2 } = fraction{ sqrt{ 2 * 0.33**2+2 * 0.03**2 - 0.31**2 } }{ 2 } = 0.175 ; ;
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