Question

A point on the terminal side of an angel theta is given. Find the exact value of the indicated trigometric function

(-1/5,1/2 ) find cos theta

Answer 1

your given point is in quad II, so the cosine of the angle will have to negative.
x = -1/5 , y = 1/2
r^2 = 1/25 + 1/4 = 29/100
r = √29/10

cosØ = x/r = (-1/5)/(√29/10)
= (-1/5)(10/√29)
= -2/√29

they might expect it to be rationalized and want the answer as -2√29/29

Answer 2

cuz you know that the angle is in the top left
you can use tan(x) = y/x to calculate the angle(it must be bigger than 90)
than use cos(x) on your cal to find cos(x)


or
you can use x^2 + y^2 = hyp^2
to find the hyp and do (-1/5)/(hyp length)
to get cos(x)