# 7 13 18 triangle

### Obtuse scalene triangle.

Sides: a = 7   b = 13   c = 18

Area: T = 36.98664840178
Perimeter: p = 38
Semiperimeter: s = 19

Angle ∠ A = α = 18.42986696038° = 18°25'43″ = 0.32216409613 rad
Angle ∠ B = β = 35.95105676196° = 35°57'2″ = 0.62774557729 rad
Angle ∠ C = γ = 125.6210762777° = 125°37'15″ = 2.19224959193 rad

Height: ha = 10.56875668622
Height: hb = 5.69902283104
Height: hc = 4.11096093353

Median: ma = 15.3055227865
Median: mb = 12.01104121495
Median: mc = 5.29215026221

Inradius: r = 1.94766570536
Circumradius: R = 11.07216119922

Vertex coordinates: A[18; 0] B[0; 0] C[5.66766666667; 4.11096093353]
Centroid: CG[7.88988888889; 1.37698697784]
Coordinates of the circumscribed circle: U[9; -6.44883014899]
Coordinates of the inscribed circle: I[6; 1.94766570536]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 161.5711330396° = 161°34'17″ = 0.32216409613 rad
∠ B' = β' = 144.049943238° = 144°2'58″ = 0.62774557729 rad
∠ C' = γ' = 54.37992372234° = 54°22'45″ = 2.19224959193 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.