Find the sin(Θ) of an angle in standard position if the terminal side passes through the point (4, -8).

Answer 1

recall sinØ = y/r

from the given: r^2 = 4^2 + (-8)^2 = 80
r = √80 = 4√5

since (4,-8) is in quad IV , and in IV the sine is negative,
sinØ = -8/4√5 = -2/√5
or -2√5/5