If the cos θ= 1/2, in the fourth quadrant, find sin θ.

The sat and act tests use very different grading scales. the sat math scores follow a normal distribution with mean 518 and standard deviation of 118. the act math scores follow a normal distribution with mean 20.7 and standard deviation of 5. suppose regan scores a 754 on the math portion of the sat. how much would her sister veronica need to score on the math portion of the act to meet or beat regan's score?

Can you me find the missing length. i attached an image.

If the value of cos330°is√3/2 then find cos 165°.