1 2 2 triangle

Acute isosceles triangle.

Sides: a = 1   b = 2   c = 2

Area: T = 0.96882458366
Perimeter: p = 5
Semiperimeter: s = 2.5

Angle ∠ A = α = 28.95550243719° = 28°57'18″ = 0.50553605103 rad
Angle ∠ B = β = 75.52224878141° = 75°31'21″ = 1.31881160717 rad
Angle ∠ C = γ = 75.52224878141° = 75°31'21″ = 1.31881160717 rad

Height: ha = 1.93664916731
Height: hb = 0.96882458366
Height: hc = 0.96882458366

Median: ma = 1.93664916731
Median: mb = 1.22547448714
Median: mc = 1.22547448714

Inradius: r = 0.38772983346
Circumradius: R = 1.0332795559

Vertex coordinates: A[2; 0] B[0; 0] C[0.25; 0.96882458366]
Centroid: CG[0.75; 0.32327486122]
Coordinates of the circumscribed circle: U[1; 0.25881988897]
Coordinates of the inscribed circle: I[0.5; 0.38772983346]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 151.0454975628° = 151°2'42″ = 0.50553605103 rad
∠ B' = β' = 104.4787512186° = 104°28'39″ = 1.31881160717 rad
∠ C' = γ' = 104.4787512186° = 104°28'39″ = 1.31881160717 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 = 1 ; ; b = 2 ; ; c = 2 ; ;

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

p = a+b+c = 1+2+2 = 5 ; ;

2. Semiperimeter of the triangle

s = fraction{ o }{ 2 } = fraction{ 5 }{ 2 } = 2.5 ; ;

3. The triangle area using Heron's formula

T = sqrt{ s(s-a)(s-b)(s-c) } ; ; T = sqrt{ 2.5 * (2.5-1)(2.5-2)(2.5-2) } ; ; T = sqrt{ 0.94 } = 0.97 ; ;

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

T = fraction{ a h _a }{ 2 } ; ; h _a = fraction{ 2 T }{ a } = fraction{ 2 * 0.97 }{ 1 } = 1.94 ; ; h _b = fraction{ 2 T }{ b } = fraction{ 2 * 0.97 }{ 2 } = 0.97 ; ; h _c = fraction{ 2 T }{ c } = fraction{ 2 * 0.97 }{ 2 } = 0.97 ; ;

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{ 1**2-2**2-2**2 }{ 2 * 2 * 2 } ) = 28° 57'18" ; ; beta = arccos( fraction{ b**2-a**2-c**2 }{ 2ac } ) = arccos( fraction{ 2**2-1**2-2**2 }{ 2 * 1 * 2 } ) = 75° 31'21" ; ; gamma = arccos( fraction{ c**2-a**2-b**2 }{ 2ba } ) = arccos( fraction{ 2**2-1**2-2**2 }{ 2 * 2 * 1 } ) = 75° 31'21" ; ;

6. Inradius

T = rs ; ; r = fraction{ T }{ s } = fraction{ 0.97 }{ 2.5 } = 0.39 ; ;

7. Circumradius

R = fraction{ a }{ 2 * sin( alpha ) } = fraction{ 1 }{ 2 * sin 28° 57'18" } = 1.03 ; ;




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