# 10 10 18 triangle

### Obtuse isosceles triangle.

Sides: a = 10   b = 10   c = 18

Area: T = 39.23300904919
Perimeter: p = 38
Semiperimeter: s = 19

Angle ∠ A = α = 25.84219327632° = 25°50'31″ = 0.45110268118 rad
Angle ∠ B = β = 25.84219327632° = 25°50'31″ = 0.45110268118 rad
Angle ∠ C = γ = 128.3166134474° = 128°18'58″ = 2.243953903 rad

Height: ha = 7.84660180984
Height: hb = 7.84660180984
Height: hc = 4.35988989435

Median: ma = 13.67547943312
Median: mb = 13.67547943312
Median: mc = 4.35988989435

Inradius: r = 2.06547416048
Circumradius: R = 11.47107866935

Vertex coordinates: A[18; 0] B[0; 0] C[9; 4.35988989435]
Centroid: CG[9; 1.45329663145]
Coordinates of the circumscribed circle: U[9; -7.112188775]
Coordinates of the inscribed circle: I[9; 2.06547416048]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 154.1588067237° = 154°9'29″ = 0.45110268118 rad
∠ B' = β' = 154.1588067237° = 154°9'29″ = 0.45110268118 rad
∠ C' = γ' = 51.68438655263° = 51°41'2″ = 2.243953903 rad

# 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. ### 1. The triangle circumference is the sum of the lengths of its three sides ### 2. Semiperimeter of the triangle ### 3. The triangle area using Heron's formula ### 4. Calculate the heights of the triangle from its area. ### 5. Calculation of the inner angles of the triangle using a Law of Cosines ### 6. Inradius ### 7. Circumradius ### 8. Calculation of medians #### Look also our friend's collection of math examples and problems:

See more informations about triangles or more information about solving triangles.