Question

this makes no sense.
help please?
If cos Θ = -2/5 and tan Θ > 0, what is the value of sin Θ?

Answer 1

\[\sin (\theta )=\sin \left(\cos ^{-1}\left(-\frac{2}{5}\right)\right) \]

Answer 2

\[\sin (\theta )=\frac{\sqrt{21}}{5} \]

Answer 3

i got a syntax error on my calculator. im still confused @robtobey

Answer 4

if cosine is negative, which quadrant do you think theta is in?

Answer 5

negative square root 21

negative square root 21 / 5

square root 21 / 5

square root 21 / 2

@sourwing @robtobey

Answer 6

yes, which quadrant theta is in if cosine is negative?

Answer 7

sin x = -(V21)/5 since tan x > 0. See drawing.

Answer 8

It isn't square root 21/5

Answer 9

@thu1935 so it's negative square root 21 / 5?