Triangle calculator SAS

Please enter two sides of the triangle and the included angle
°


Right isosceles triangle.

Sides: a = 0.75   b = 0.75   c = 1.06106601718

Area: T = 0.281125
Perimeter: p = 2.56106601718
Semiperimeter: s = 1.28803300859

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

Height: ha = 0.75
Height: hb = 0.75
Height: hc = 0.53303300859

Median: ma = 0.83985254916
Median: mb = 0.83985254916
Median: mc = 0.53303300859

Inradius: r = 0.22196699141
Circumradius: R = 0.53303300859

Vertex coordinates: A[1.06106601718; 0] B[0; 0] C[0.53303300859; 0.53303300859]
Centroid: CG[0.53303300859; 0.17767766953]
Coordinates of the circumscribed circle: U[0.53303300859; 0]
Coordinates of the inscribed circle: I[0.53303300859; 0.22196699141]

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

a = 0.75 ; ; b = 0.75 ; ; gamma = 90° ; ; ; ; c**2 = a**2+b**2 - 2ab cos( gamma ) ; ; c = sqrt{ a**2+b**2 - 2ab cos( gamma ) } ; ; c = sqrt{ 0.75**2+0.75**2 - 2 * 0.75 * 0.75 * cos(90° ) } ; ; c = 1.06 ; ;


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 = 0.75 ; ; b = 0.75 ; ; c = 1.06 ; ;

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

p = a+b+c = 0.75+0.75+1.06 = 2.56 ; ;

3. Semiperimeter of the triangle

s = fraction{ o }{ 2 } = fraction{ 2.56 }{ 2 } = 1.28 ; ;

4. The triangle area using Heron's formula

T = sqrt{ s(s-a)(s-b)(s-c) } ; ; T = sqrt{ 1.28 * (1.28-0.75)(1.28-0.75)(1.28-1.06) } ; ; T = sqrt{ 0.08 } = 0.28 ; ;

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

T = fraction{ a h _a }{ 2 } ; ; h _a = fraction{ 2 T }{ a } = fraction{ 2 * 0.28 }{ 0.75 } = 0.75 ; ; h _b = fraction{ 2 T }{ b } = fraction{ 2 * 0.28 }{ 0.75 } = 0.75 ; ; h _c = fraction{ 2 T }{ c } = fraction{ 2 * 0.28 }{ 1.06 } = 0.53 ; ;

6. 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{ 0.75**2-0.75**2-1.06**2 }{ 2 * 0.75 * 1.06 } ) = 45° ; ; beta = arccos( fraction{ b**2-a**2-c**2 }{ 2ac } ) = arccos( fraction{ 0.75**2-0.75**2-1.06**2 }{ 2 * 0.75 * 1.06 } ) = 45° ; ; gamma = arccos( fraction{ c**2-a**2-b**2 }{ 2ba } ) = arccos( fraction{ 1.06**2-0.75**2-0.75**2 }{ 2 * 0.75 * 0.75 } ) = 90° ; ;

7. Inradius

T = rs ; ; r = fraction{ T }{ s } = fraction{ 0.28 }{ 1.28 } = 0.22 ; ;

8. Circumradius

R = fraction{ a }{ 2 * sin( alpha ) } = fraction{ 0.75 }{ 2 * sin 45° } = 0.53 ; ;




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