Triangle calculator ASA

Please enter the side of the triangle and two adjacent angles
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Right isosceles triangle.

Sides: a = 25.45658441227   b = 25.45658441227   c = 36

Area: T = 324
Perimeter: p = 86.91216882454
Semiperimeter: s = 43.45658441227

Angle ∠ A = α = 45° = 0.78553981634 rad
Angle ∠ B = β = 45° = 0.78553981634 rad
Angle ∠ C = γ = 90° = 1.57107963268 rad

Height: ha = 25.45658441227
Height: hb = 25.45658441227
Height: hc = 18

Median: ma = 28.46604989415
Median: mb = 28.46604989415
Median: mc = 18

Inradius: r = 7.45658441227
Circumradius: R = 18

Vertex coordinates: A[36; 0] B[0; 0] C[18; 18]
Centroid: CG[18; 6]
Coordinates of the circumscribed circle: U[18; 0]
Coordinates of the inscribed circle: I[18; 7.45658441227]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 135° = 0.78553981634 rad
∠ B' = β' = 135° = 0.78553981634 rad
∠ C' = γ' = 90° = 1.57107963268 rad

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How did we calculate this triangle?

1. Calculate the third unknown inner angle

 alpha = 45° ; ; beta = 45° ; ; ; ; alpha + beta + gamma = 180° ; ; ; ; gamma = 180° - alpha - beta = 180° - 45° - 45° = 90° ; ;

2. By using the law of sines, we calculate unknown side a

c = 36 ; ; ; ; fraction{ a }{ c } = fraction{ sin( alpha ) }{ sin ( gamma ) } ; ; ; ; a = c * fraction{ sin( alpha ) }{ sin ( gamma ) } ; ; ; ; a = 36 * fraction{ sin(45° ) }{ sin (90° ) } = 25.46 ; ;

3. By using the law of sines, we calculate last unknown side b

 fraction{ b }{ c } = fraction{ sin( beta ) }{ sin ( gamma ) } ; ; ; ; b = c * fraction{ sin( beta ) }{ sin ( gamma ) } ; ; ; ; b = 36 * fraction{ sin(45° ) }{ sin (90° ) } = 25.46 ; ;


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 = 25.46 ; ; b = 25.46 ; ; c = 36 ; ;

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

p = a+b+c = 25.46+25.46+36 = 86.91 ; ;

5. Semiperimeter of the triangle

s = fraction{ o }{ 2 } = fraction{ 86.91 }{ 2 } = 43.46 ; ;

6. The triangle area using Heron's formula

T = sqrt{ s(s-a)(s-b)(s-c) } ; ; T = sqrt{ 43.46 * (43.46-25.46)(43.46-25.46)(43.46-36) } ; ; T = sqrt{ 104976 } = 324 ; ;

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

T = fraction{ a h _a }{ 2 } ; ; h _a = fraction{ 2 T }{ a } = fraction{ 2 * 324 }{ 25.46 } = 25.46 ; ; h _b = fraction{ 2 T }{ b } = fraction{ 2 * 324 }{ 25.46 } = 25.46 ; ; h _c = fraction{ 2 T }{ c } = fraction{ 2 * 324 }{ 36 } = 18 ; ;

8. 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{ 25.46**2-25.46**2-36**2 }{ 2 * 25.46 * 36 } ) = 45° ; ; beta = arccos( fraction{ b**2-a**2-c**2 }{ 2ac } ) = arccos( fraction{ 25.46**2-25.46**2-36**2 }{ 2 * 25.46 * 36 } ) = 45° ; ; gamma = arccos( fraction{ c**2-a**2-b**2 }{ 2ba } ) = arccos( fraction{ 36**2-25.46**2-25.46**2 }{ 2 * 25.46 * 25.46 } ) = 90° ; ;

9. Inradius

T = rs ; ; r = fraction{ T }{ s } = fraction{ 324 }{ 43.46 } = 7.46 ; ;

10. Circumradius

R = fraction{ a }{ 2 * sin( alpha ) } = fraction{ 25.46 }{ 2 * sin 45° } = 18 ; ;




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