Ugh, More Trig Stuff

Quote:

Originally Posted by aussiekid90

Another question i had was: If sin(alpha)=4/5 in quadrant 1 and
cos(beta)=-11/12 in quadrant II, find

Sin(alpha+beta)

Tan(alpha+beta)

Thats a LOT for the help.

You could get fancy and use the sum of angles formulas, but I think it's easier just to find alpha and beta:
$\alpha = sin^{-1} \left ( \frac{4}{5} \right ) \approx 0.927295 \, rad$
$\alpha$ is supposed to be 1st quadrant and, in fact, it is.

$\beta = cos^{-1} \left ( - \frac{11}{12} \right ) \approx 2.73045 \, rad$
which checks out as being in the 2nd quadrant.

So:
$sin(\alpha + \beta) = sin(3.65775)=-0.493542$
$tan(\alpha + \beta) = tan(3.65775) = 0.567471$

-Dan