If 𝑐𝑜𝑠50∘=𝑎, what is 𝑠𝑖𝑛40∘ in terms of a?

The relationship between sine and cosine for complementary angles can be used to solve this problem. The angles 50° and 40° are complementary because they add up to 90°.

The sine of an angle is equal to the cosine of its complement. Therefore, sin(40°) is equal to cos(50°).

So, if cos(50°) = a, then sin(40°) = a as well.