# How do you find the missing length of an isosceles triangle given Base = 20 Angle = 25?

Use trig identity: $\frac{a}{\sin} A = \frac{b}{\sin} B$
$c = b = \left(a . \sin B\right) \sin A = \left(25\right) \frac{0.42}{0.64} = 16.40$