Can someone explain to me how this is done?
Find the exact of sin 20, cos 20, tan 20 for the angle described below.
cos 20=24/25
The terminal side of 0 lies in quadrant IV
draw a diagram. you have a right-triangle with an acute angle being 20. cosine = adjacent/hypotenuse. so the side adjacent to the 20 degree angle is 24 and the hypotenuse is 25. You can find the remaining side using Pythagoras' theorem.
Now to find the sine and tangent. Recall that sine = opposite/hypotenuse and tangent = opposite/adjacent
we are in the fourth quad, so sine and tangent are negative
alternatively, you could use formulas. $\displaystyle \sin^2 x + \cos^2 x = 1$ and $\displaystyle \tan x = \frac {\sin x}{\cos x}$