# 1 9 9 triangle

### Acute isosceles triangle.

Sides: a = 1   b = 9   c = 9

Area: T = 4.49330501889
Perimeter: p = 19
Semiperimeter: s = 9.5

Angle ∠ A = α = 6.36994770734° = 6°22'10″ = 0.11111683466 rad
Angle ∠ B = β = 86.81552614633° = 86°48'55″ = 1.51552121535 rad
Angle ∠ C = γ = 86.81552614633° = 86°48'55″ = 1.51552121535 rad

Height: ha = 8.98661003778
Height: hb = 0.99884555975
Height: hc = 0.99884555975

Median: ma = 8.98661003778
Median: mb = 4.55552167896
Median: mc = 4.55552167896

Inradius: r = 0.47329526515
Circumradius: R = 4.5076960561

Vertex coordinates: A[9; 0] B[0; 0] C[0.05655555556; 0.99884555975]
Centroid: CG[3.01985185185; 0.33328185325]
Coordinates of the circumscribed circle: U[4.5; 0.25503866978]
Coordinates of the inscribed circle: I[0.5; 0.47329526515]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 173.6310522927° = 173°37'50″ = 0.11111683466 rad
∠ B' = β' = 93.18547385367° = 93°11'5″ = 1.51552121535 rad
∠ C' = γ' = 93.18547385367° = 93°11'5″ = 1.51552121535 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.