Question

Suppose an isosceles triangle ABC has A = 45° and b = c = 4. What is the length of a^2?

Answer 1

Since b = c, the angles B and C are congruent.
180 - 45 = 135
135/2 = =67.5

A = 45
B = 67.5
C = 67.5
a = ?
b = 4
c = 4

Since we know two sides and all three angles, we can use the law of sines to find a.

b/sin B = a/sin A

4/(sin 67.5) = a/(sin 45)

a = 4(sin 45)/(sin 67.5)

a^2 = (4(sin 45)/(sin 67.5))^2

a^2 = 9.37