Question

Multiple choice. Use the Law of Sines to find the missing angle of the triangle. Find m angle C to the nearest tenth if c = 111 a = 42, and m angle A=22 .

A. 81.9
B. 98.1

Answer 1

Both A and B are possible.

Explanation:

It's both!

This is a might tricky. First you have to find the altitude. You have to determine if this is a real triangle.

Sin(22) = opposite / hypotenuse. The hypotenuse = 111. The angle is 22

opposite = hypotenuse * sin(22)

opposite = 111 * sin(22)

opposite = 41.58 and this is the altitude.

What have you learned?

Since 42 is larger than 41.58 you have 2 solutions to the triangle. One of the angles is acute, and the other one is obtuse. They are supplementary angles.

Sin(C) / c = Sin(A) / a

Sin(C) = c * Sin(22) / 42

Sin(C) = 111*sin(22)/ 42

Sin(C) = .99003

Sin(C) = 81.9

So that's your first answer. The second answer comes from Finding the supplement to this angle

supplement + 81.9 = 180

supplement = 180 - 81.9

supplement = 98.1