In a ∆ABC, if b = 20, c = 21 and sin A = 3/5, find a

Question

In a ∆ABC, if b = 20, c = 21 and sin A = \(\cfrac35\), find a.

Answer 1

We know,

Now by putting cosine law

By Cosine law,

a² =400 + 441 - 672

=169

a = 13