# 3 7 9 triangle

### Obtuse scalene triangle.

Sides: a = 3   b = 7   c = 9

Area: T = 8.78656416954
Perimeter: p = 19
Semiperimeter: s = 9.5

Angle ∠ A = α = 16.1955116739° = 16°11'42″ = 0.28326581098 rad
Angle ∠ B = β = 40.60110607311° = 40°36'4″ = 0.70986221896 rad
Angle ∠ C = γ = 123.204382253° = 123°12'14″ = 2.15503123542 rad

Height: ha = 5.85770944636
Height: hb = 2.51101833415
Height: hc = 1.95223648212

Median: ma = 7.92114897589
Median: mb = 5.72327615711
Median: mc = 2.95880398915

Inradius: r = 0.9254804389
Circumradius: R = 5.3788093216

Vertex coordinates: A[9; 0] B[0; 0] C[2.27877777778; 1.95223648212]
Centroid: CG[3.75992592593; 0.65107882737]
Coordinates of the circumscribed circle: U[4.5; -2.94551462849]
Coordinates of the inscribed circle: I[2.5; 0.9254804389]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 163.8054883261° = 163°48'18″ = 0.28326581098 rad
∠ B' = β' = 139.3998939269° = 139°23'56″ = 0.70986221896 rad
∠ C' = γ' = 56.796617747° = 56°47'46″ = 2.15503123542 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.