Equilateral triangle calculator

Please enter one property of the equilateral triangle

Use symbols: a, h, T, p, r, R


You have entered side a, b and c (as equilateral triangle).

Equilateral triangle.

Sides: a = 0.52986   b = 0.52986   c = 0.52986

Area: T = 0.12109915258
Perimeter: p = 1.58658
Semiperimeter: s = 0.79329

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

Height: ha = 0.45877810284
Height: hb = 0.45877810284
Height: hc = 0.45877810284

Median: ma = 0.45877810284
Median: mb = 0.45877810284
Median: mc = 0.45877810284

Inradius: r = 0.15325936761
Circumradius: R = 0.30551873523

Vertex coordinates: A[0.52986; 0] B[0; 0] C[0.26443; 0.45877810284]
Centroid: CG[0.26443; 0.15325936761]
Coordinates of the circumscribed circle: U[0.26443; 0.15325936761]
Coordinates of the inscribed circle: I[0.26443; 0.15325936761]

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?

1. Input data entered: side a b c (as equilateral triangle)

a = 0.529 ; ; b = 0.529 ; ; c = 0.529 ; ;

2. From we calculate b,c:

b = c = a = 0.529 ; ;


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 = 0.53 ; ; b = 0.53 ; ; c = 0.53 ; ;

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

p = a+b+c = 0.53+0.53+0.53 = 1.59 ; ;

4. Semiperimeter of the triangle

s = fraction{ o }{ 2 } = fraction{ 1.59 }{ 2 } = 0.79 ; ;

5. The triangle area using Heron's formula

T = sqrt{ s(s-a)(s-b)(s-c) } ; ; T = sqrt{ 0.79 * (0.79-0.53)(0.79-0.53)(0.79-0.53) } ; ; T = sqrt{ 0.01 } = 0.12 ; ;

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

T = fraction{ a h _a }{ 2 } ; ; h _a = fraction{ 2 T }{ a } = fraction{ 2 * 0.12 }{ 0.53 } = 0.46 ; ; h _b = fraction{ 2 T }{ b } = fraction{ 2 * 0.12 }{ 0.53 } = 0.46 ; ; h _c = fraction{ 2 T }{ c } = fraction{ 2 * 0.12 }{ 0.53 } = 0.46 ; ;

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{ a**2-b**2-c**2 }{ 2bc } ) = arccos( fraction{ 0.53**2-0.53**2-0.53**2 }{ 2 * 0.53 * 0.53 } ) = 60° ; ; beta = arccos( fraction{ b**2-a**2-c**2 }{ 2ac } ) = arccos( fraction{ 0.53**2-0.53**2-0.53**2 }{ 2 * 0.53 * 0.53 } ) = 60° ; ; gamma = arccos( fraction{ c**2-a**2-b**2 }{ 2ba } ) = arccos( fraction{ 0.53**2-0.53**2-0.53**2 }{ 2 * 0.53 * 0.53 } ) = 60° ; ;

8. Inradius

T = rs ; ; r = fraction{ T }{ s } = fraction{ 0.12 }{ 0.79 } = 0.15 ; ;

9. Circumradius

R = fraction{ a }{ 2 * sin( alpha ) } = fraction{ 0.53 }{ 2 * sin 60° } = 0.31 ; ;




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