# 9 9 12 triangle

### Acute isosceles triangle.

Sides: a = 9   b = 9   c = 12

Area: T = 40.2499223595
Perimeter: p = 30
Semiperimeter: s = 15

Angle ∠ A = α = 48.19896851042° = 48°11'23″ = 0.84110686706 rad
Angle ∠ B = β = 48.19896851042° = 48°11'23″ = 0.84110686706 rad
Angle ∠ C = γ = 83.62106297916° = 83°37'14″ = 1.45994553125 rad

Height: ha = 8.944427191
Height: hb = 8.944427191
Height: hc = 6.70882039325

Median: ma = 9.60546863561
Median: mb = 9.60546863561
Median: mc = 6.70882039325

Inradius: r = 2.6833281573
Circumradius: R = 6.03773835392

Vertex coordinates: A[12; 0] B[0; 0] C[6; 6.70882039325]
Centroid: CG[6; 2.23660679775]
Coordinates of the circumscribed circle: U[6; 0.67108203932]
Coordinates of the inscribed circle: I[6; 2.6833281573]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 131.8110314896° = 131°48'37″ = 0.84110686706 rad
∠ B' = β' = 131.8110314896° = 131°48'37″ = 0.84110686706 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.