# 2 9 9 triangle

### Acute isosceles triangle.

Sides: a = 2   b = 9   c = 9

Area: T = 8.944427191
Perimeter: p = 20
Semiperimeter: s = 10

Angle ∠ A = α = 12.75987404169° = 12°45'31″ = 0.22326820287 rad
Angle ∠ B = β = 83.62106297916° = 83°37'14″ = 1.45994553125 rad
Angle ∠ C = γ = 83.62106297916° = 83°37'14″ = 1.45994553125 rad

Height: ha = 8.944427191
Height: hb = 1.988761598
Height: hc = 1.988761598

Median: ma = 8.944427191
Median: mb = 4.7176990566
Median: mc = 4.7176990566

Inradius: r = 0.8944427191
Circumradius: R = 4.52880376544

Vertex coordinates: A[9; 0] B[0; 0] C[0.22222222222; 1.988761598]
Centroid: CG[3.07440740741; 0.663253866]
Coordinates of the circumscribed circle: U[4.5; 0.50331152949]
Coordinates of the inscribed circle: I[1; 0.8944427191]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 167.2411259583° = 167°14'29″ = 0.22326820287 rad
∠ B' = β' = 96.37993702084° = 96°22'46″ = 1.45994553125 rad
∠ C' = γ' = 96.37993702084° = 96°22'46″ = 1.45994553125 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.