Question

Given: a = 640, A = 70°, B = 52° in triangle ABC ; find c . Round answers to the nearest whole number. Do not use a decimal point or extra spaces in the answer or it will be marked incorrect.

Answer 1

Law of sines:
$\frac{a}{\sin A}=\frac{b}{\sin B}=\frac{c}{\sin C}\\=\frac{640}{\sin 70}=\frac{c}{\sin (180-70-52)}\\\text{ then}\\c=\frac{640}{\sin 70}\sin (180-70-52)\\=577$