Triangle calculator VC

Please enter the coordinates of the three vertices


Right isosceles triangle.

Sides: a = 17.20546505341   b = 12.16655250606   c = 12.16655250606

Area: T = 74
Perimeter: p = 41.53657006553
Semiperimeter: s = 20.76878503276

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

Height: ha = 8.6022325267
Height: hb = 12.16655250606
Height: hc = 12.16655250606

Median: ma = 8.6022325267
Median: mb = 13.60114705087
Median: mc = 13.60114705087

Inradius: r = 3.56331997936
Circumradius: R = 8.6022325267

Vertex coordinates: A[3; -6] B[1; 6] C[-9; -8]
Centroid: CG[-1.66766666667; -2.66766666667]
Coordinates of the circumscribed circle: U[0; 0]
Coordinates of the inscribed circle: I[3.56331997936; 3.56331997936]

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

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How did we calculate this triangle?

1. We compute side a from coordinates using the Pythagorean theorem

a = | beta gamma | = | beta - gamma | ; ; a**2 = ( beta _x- gamma _x)**2 + ( beta _y- gamma _y)**2 ; ; a = sqrt{ ( beta _x- gamma _x)**2 + ( beta _y- gamma _y)**2 } ; ; a = sqrt{ (1-(-9))**2 + (6-(-8))**2 } ; ; a = sqrt{ 296 } = 17.2 ; ;

2. We compute side b from coordinates using the Pythagorean theorem

b = | alpha gamma | = | alpha - gamma | ; ; b**2 = ( alpha _x- gamma _x)**2 + ( alpha _y- gamma _y)**2 ; ; b = sqrt{ ( alpha _x- gamma _x)**2 + ( alpha _y- gamma _y)**2 } ; ; b = sqrt{ (3-(-9))**2 + (-6-(-8))**2 } ; ; b = sqrt{ 148 } = 12.17 ; ;

3. We compute side c from coordinates using the Pythagorean theorem

c = | alpha beta | = | alpha - beta | ; ; c**2 = ( alpha _x- beta _x)**2 + ( alpha _y- beta _y)**2 ; ; c = sqrt{ ( alpha _x- beta _x)**2 + ( alpha _y- beta _y)**2 } ; ; c = sqrt{ (3-1)**2 + (-6-6)**2 } ; ; c = sqrt{ 148 } = 12.17 ; ;


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 = 17.2 ; ; b = 12.17 ; ; c = 12.17 ; ;

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

p = a+b+c = 17.2+12.17+12.17 = 41.54 ; ;

5. Semiperimeter of the triangle

s = fraction{ o }{ 2 } = fraction{ 41.54 }{ 2 } = 20.77 ; ;

6. The triangle area using Heron's formula

T = sqrt{ s(s-a)(s-b)(s-c) } ; ; T = sqrt{ 20.77 * (20.77-17.2)(20.77-12.17)(20.77-12.17) } ; ; T = sqrt{ 5476 } = 74 ; ;

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

T = fraction{ a h _a }{ 2 } ; ; h _a = fraction{ 2 T }{ a } = fraction{ 2 * 74 }{ 17.2 } = 8.6 ; ; h _b = fraction{ 2 T }{ b } = fraction{ 2 * 74 }{ 12.17 } = 12.17 ; ; h _c = fraction{ 2 T }{ c } = fraction{ 2 * 74 }{ 12.17 } = 12.17 ; ;

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{ 17.2**2-12.17**2-12.17**2 }{ 2 * 12.17 * 12.17 } ) = 90° ; ; beta = arccos( fraction{ b**2-a**2-c**2 }{ 2ac } ) = arccos( fraction{ 12.17**2-17.2**2-12.17**2 }{ 2 * 17.2 * 12.17 } ) = 45° ; ; gamma = arccos( fraction{ c**2-a**2-b**2 }{ 2ba } ) = arccos( fraction{ 12.17**2-17.2**2-12.17**2 }{ 2 * 12.17 * 17.2 } ) = 45° ; ;

9. Inradius

T = rs ; ; r = fraction{ T }{ s } = fraction{ 74 }{ 20.77 } = 3.56 ; ;

10. Circumradius

R = fraction{ a }{ 2 * sin( alpha ) } = fraction{ 17.2 }{ 2 * sin 90° } = 8.6 ; ;




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