# 9 21 26 triangle

### Obtuse scalene triangle.

Sides: a = 9   b = 21   c = 26

Area: T = 86.30217960416
Perimeter: p = 56
Semiperimeter: s = 28

Angle ∠ A = α = 18.42986696038° = 18°25'43″ = 0.32216409613 rad
Angle ∠ B = β = 47.52992544904° = 47°31'45″ = 0.83295419819 rad
Angle ∠ C = γ = 114.0422075906° = 114°2'31″ = 1.99904097104 rad

Height: ha = 19.17881768981
Height: hb = 8.21992186706
Height: hc = 6.63985996955

Median: ma = 23.22002155162
Median: mb = 16.37883393542
Median: mc = 9.59216630466

Inradius: r = 3.08222070015
Circumradius: R = 14.23549297042

Vertex coordinates: A[26; 0] B[0; 0] C[6.07769230769; 6.63985996955]
Centroid: CG[10.69223076923; 2.21328665652]
Coordinates of the circumscribed circle: U[13; -5.79994158054]
Coordinates of the inscribed circle: I[7; 3.08222070015]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 161.5711330396° = 161°34'17″ = 0.32216409613 rad
∠ B' = β' = 132.471074551° = 132°28'15″ = 0.83295419819 rad
∠ C' = γ' = 65.95879240942° = 65°57'29″ = 1.99904097104 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.