# 11 11 21 triangle

### Obtuse isosceles triangle.

Sides: a = 11   b = 11   c = 21

Area: T = 34.42765522526
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 17.34114428028° = 17°20'29″ = 0.3032665274 rad
Angle ∠ B = β = 17.34114428028° = 17°20'29″ = 0.3032665274 rad
Angle ∠ C = γ = 145.3177114394° = 145°19'2″ = 2.53662621057 rad

Height: ha = 6.25993731368
Height: hb = 6.25993731368
Height: hc = 3.27987192622

Median: ma = 15.83550876221
Median: mb = 15.83550876221
Median: mc = 3.27987192622

Inradius: r = 1.60112349885
Circumradius: R = 18.45223270102

Vertex coordinates: A[21; 0] B[0; 0] C[10.5; 3.27987192622]
Centroid: CG[10.5; 1.09329064207]
Coordinates of the circumscribed circle: U[10.5; -15.17436077481]
Coordinates of the inscribed circle: I[10.5; 1.60112349885]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 162.6598557197° = 162°39'31″ = 0.3032665274 rad
∠ B' = β' = 162.6598557197° = 162°39'31″ = 0.3032665274 rad
∠ C' = γ' = 34.68328856055° = 34°40'58″ = 2.53662621057 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.