3 3 3 triangle

Equilateral triangle.

Sides: a = 3   b = 3   c = 3

Area: T = 3.8977114317
Perimeter: p = 9
Semiperimeter: s = 4.5

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

Height: ha = 2.59880762114
Height: hb = 2.59880762114
Height: hc = 2.59880762114

Median: ma = 2.59880762114
Median: mb = 2.59880762114
Median: mc = 2.59880762114

Inradius: r = 0.86660254038
Circumradius: R = 1.73220508076

Vertex coordinates: A[3; 0] B[0; 0] C[1.5; 2.59880762114]
Centroid: CG[1.5; 0.86660254038]
Coordinates of the circumscribed circle: U[1.5; 0.86660254038]
Coordinates of the inscribed circle: I[1.5; 0.86660254038]

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?

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 = 3 ; ; b = 3 ; ; c = 3 ; ;

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

p = a+b+c = 3+3+3 = 9 ; ;

2. Semiperimeter of the triangle

s = fraction{ o }{ 2 } = fraction{ 9 }{ 2 } = 4.5 ; ;

3. The triangle area using Heron's formula

T = sqrt{ s(s-a)(s-b)(s-c) } ; ; T = sqrt{ 4.5 * (4.5-3)(4.5-3)(4.5-3) } ; ; T = sqrt{ 15.19 } = 3.9 ; ;

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

T = fraction{ a h _a }{ 2 } ; ; h _a = fraction{ 2 T }{ a } = fraction{ 2 * 3.9 }{ 3 } = 2.6 ; ; h _b = fraction{ 2 T }{ b } = fraction{ 2 * 3.9 }{ 3 } = 2.6 ; ; h _c = fraction{ 2 T }{ c } = fraction{ 2 * 3.9 }{ 3 } = 2.6 ; ;

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{ 3**2-3**2-3**2 }{ 2 * 3 * 3 } ) = 60° ; ; beta = arccos( fraction{ b**2-a**2-c**2 }{ 2ac } ) = arccos( fraction{ 3**2-3**2-3**2 }{ 2 * 3 * 3 } ) = 60° ; ; gamma = arccos( fraction{ c**2-a**2-b**2 }{ 2ba } ) = arccos( fraction{ 3**2-3**2-3**2 }{ 2 * 3 * 3 } ) = 60° ; ;

6. Inradius

T = rs ; ; r = fraction{ T }{ s } = fraction{ 3.9 }{ 4.5 } = 0.87 ; ;

7. Circumradius

R = fraction{ a }{ 2 * sin( alpha ) } = fraction{ 3 }{ 2 * sin 60° } = 1.73 ; ;




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