Question

A viewfinder has a triangular Lens. Some of the measurements of the lens are shown below . Which of the following best represents the length of a

Answer 1

The sum of angles in a triangle is  180°. Therefore
m∠M = 180 - (38 + 32) = 110°

We now have b=7, m∠A=38°, m∠B=110°.

Apply the Law of Sines.
$\frac{a}{sinA} = \frac{b}{sinB}$
$\frac{a}{sin(38)} = \frac{7}{sin(110)}$
$a=7[ \frac{sin(38)}{sin(110)}]=4.586$

Answer:
a = 4.6 (nearest tenth)