# 18 18 26 triangle

### Obtuse isosceles triangle.

Sides: a = 18   b = 18   c = 26

Area: T = 161.8498694774
Perimeter: p = 62
Semiperimeter: s = 31

Angle ∠ A = α = 43.76217426927° = 43°45'42″ = 0.76437864964 rad
Angle ∠ B = β = 43.76217426927° = 43°45'42″ = 0.76437864964 rad
Angle ∠ C = γ = 92.47765146146° = 92°28'35″ = 1.61440196608 rad

Height: ha = 17.98331883082
Height: hb = 17.98331883082
Height: hc = 12.4549899598

Median: ma = 20.46994894905
Median: mb = 20.46994894905
Median: mc = 12.4549899598

Inradius: r = 5.22109256379
Circumradius: R = 13.01221531282

Vertex coordinates: A[26; 0] B[0; 0] C[13; 12.4549899598]
Centroid: CG[13; 4.15499665327]
Coordinates of the circumscribed circle: U[13; -0.56222535302]
Coordinates of the inscribed circle: I[13; 5.22109256379]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 136.2388257307° = 136°14'18″ = 0.76437864964 rad
∠ B' = β' = 136.2388257307° = 136°14'18″ = 0.76437864964 rad
∠ C' = γ' = 87.52334853854° = 87°31'25″ = 1.61440196608 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.