Exercise 4 Page 911

We want to find the exact value of sinθ given that cosθ = - 35. To do so, we will use one of the Pythagorean Identities. Note that we will need to rearrange the terms so that we can use it for our expression. cos ^2 θ +sin ^2 θ=1 ⇕ 1-cos^2θ = sin^2θ Let's do it!

Be aware that we are told that θ lies between 90^(∘) and 180^(∘). Therefore, θ is in Quadrant II.

In this quadrant, the sine of θ is positive. Therefore, we will only keep the positive solution. sin θ =4/5