Question

Use the information given to determine cos 2x.

sin x = -0.1

Round your answer to three decimal places.

Answer 1

0.98

When you see this kind of problem, try to see how cos 2x and sin x relate--don't go straight to finding x because it is unnecessary. In this case, there is a formula that shows the relationship between cos 2x and sin x as shown:

cos 2x = 1 - 2(sin x)^2

All we have to do is plug in the value of sin x to find the value of cos 2x.

cos 2x = 1 - 2(-0.1)^2 = 1 - 2(0.01) = 1 - 0.02 = 0.98