Question

If sinx = 0.3, and x is in Quadrant III, then what is the value of cosx?

Answer 1

Probably the question should say $\sin x=-0.3$, as $\sin x$ is negative for $\pi$.

In that case, recall that

$\cos^2x+\sin^2x=1\implies\cos x=\pm\sqrt{1-\sin^2x}$

Because $x$ lies in the third quadrant, we expect $\cos x$ to also be negative, so we take the negative root above. Then

$\cos x=-\sqrt{1-(-0.3)^2}\approx-0.954$

Answer 2

SOS

Answer:

Use the trig identities: SOH CAH TOA

• sin(x) = 0.3
• cos(x) = √0.9

Hope this helps!!!

$Sofia$