# 1 21 21 triangle

### Acute isosceles triangle.

Sides: a = 1   b = 21   c = 21

Area: T = 10.49770233876
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 2.72986283013° = 2°43'43″ = 0.04876235479 rad
Angle ∠ B = β = 88.63656858493° = 88°38'8″ = 1.54769845528 rad
Angle ∠ C = γ = 88.63656858493° = 88°38'8″ = 1.54769845528 rad

Height: ha = 20.99440467752
Height: hb = 10.9997165131
Height: hc = 10.9997165131

Median: ma = 20.99440467752
Median: mb = 10.52437825899
Median: mc = 10.52437825899

Inradius: r = 0.48882336459
Circumradius: R = 10.50329774565

Vertex coordinates: A[21; 0] B[0; 0] C[0.02438095238; 10.9997165131]
Centroid: CG[7.00879365079; 0.33332388377]
Coordinates of the circumscribed circle: U[10.5; 0.25500708918]
Coordinates of the inscribed circle: I[0.5; 0.48882336459]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 177.2711371699° = 177°16'17″ = 0.04876235479 rad
∠ B' = β' = 91.36443141507° = 91°21'52″ = 1.54769845528 rad
∠ C' = γ' = 91.36443141507° = 91°21'52″ = 1.54769845528 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.