Triangle calculator

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

You have entered side a, b and c.

Equilateral triangle.

Sides: a = 70   b = 70   c = 70

Area: T = 2121.762223927
Perimeter: p = 210
Semiperimeter: s = 105

Angle ∠ A = α = 60° = 1.04771975512 rad
Angle ∠ B = β = 60° = 1.04771975512 rad
Angle ∠ C = γ = 60° = 1.04771975512 rad

Height: ha = 60.62217782649
Height: hb = 60.62217782649
Height: hc = 60.62217782649

Median: ma = 60.62217782649
Median: mb = 60.62217782649
Median: mc = 60.62217782649

Inradius: r = 20.20772594216
Circumradius: R = 40.41545188433

Vertex coordinates: A[70; 0] B[0; 0] C[35; 60.62217782649]
Centroid: CG[35; 20.20772594216]
Coordinates of the circumscribed circle: U[35; 20.20772594216]
Coordinates of the inscribed circle: I[35; 20.20772594216]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 120° = 1.04771975512 rad
∠ B' = β' = 120° = 1.04771975512 rad
∠ C' = γ' = 120° = 1.04771975512 rad

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How did we calculate this triangle?

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 = 70 ; ; b = 70 ; ; c = 70 ; ;

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

p = a+b+c = 70+70+70 = 210 ; ;

2. Semiperimeter of the triangle

s = fraction{ o }{ 2 } = fraction{ 210 }{ 2 } = 105 ; ;

3. The triangle area using Heron's formula

T = sqrt{ s(s-a)(s-b)(s-c) } ; ; T = sqrt{ 105 * (105-70)(105-70)(105-70) } ; ; T = sqrt{ 4501875 } = 2121.76 ; ;

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

T = fraction{ a h _a }{ 2 } ; ; h _a = fraction{ 2 T }{ a } = fraction{ 2 * 2121.76 }{ 70 } = 60.62 ; ; h _b = fraction{ 2 T }{ b } = fraction{ 2 * 2121.76 }{ 70 } = 60.62 ; ; h _c = fraction{ 2 T }{ c } = fraction{ 2 * 2121.76 }{ 70 } = 60.62 ; ;

5. 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{ a**2-b**2-c**2 }{ 2bc } ) = arccos( fraction{ 70**2-70**2-70**2 }{ 2 * 70 * 70 } ) = 60° ; ; beta = arccos( fraction{ b**2-a**2-c**2 }{ 2ac } ) = arccos( fraction{ 70**2-70**2-70**2 }{ 2 * 70 * 70 } ) = 60° ; ; gamma = arccos( fraction{ c**2-a**2-b**2 }{ 2ba } ) = arccos( fraction{ 70**2-70**2-70**2 }{ 2 * 70 * 70 } ) = 60° ; ;

6. Inradius

T = rs ; ; r = fraction{ T }{ s } = fraction{ 2121.76 }{ 105 } = 20.21 ; ;

7. Circumradius

R = fraction{ a }{ 2 * sin( alpha ) } = fraction{ 70 }{ 2 * sin 60° } = 40.41 ; ;




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