How to find the side of isosceles triangle

Isosceles is called a triangle whose 2 sides are equal. From the definition it follows that a right triangle is also isosceles, but the converse is wrong. There are several ways to calculate the sides of an isosceles triangle.

You will need

• Know the angles of a triangle and at least one of its sides.

Instruction

1. Method 1. Out of the theorem of sines of a triangle. The theorem of sines States that: the sides of the triangle are proportional to the sines of the opposite angles (Fig. 1)
   From this formula implies the following equality:a = 2Rsinα,b = 2Rsinβ
   
2. Method 2. Out of the cosines of the triangle. According to this theorem, for any plane triangle with sides a, b, c and angle α, which lies opposite the side, true equality in Fig. 2
   Hence, there is a consequence:a = b/2cosα;
   Also from the theorem of cosines, there is 1 more result:
   b = 2a*sin(β/2)