If cos theta = -4/7, what are the values of sin theta and tan theta

Cos theta = adjacent side   /   hypotenuse  =  -4/7   (hyp is always positive).
Thus, the adj. side is -4 when the hyp is 7.

Using the Pyth. Thm. to find the opp side:

(opp side)^2 + (adj side)^2 = (hyp)^2, or

(opp side)^2 + (-4)^2 = 7^2 = 49.  Then (opp)^2 +16 = 49, and (opp)^2 = 33.

Then (opp side) = plus or minus sqrt(33)

Because cos theta = -4/7 is negative, theta is in either Quadrant II or Q III.

If in Q II, the opp side will be positive, so the sine of theta is +sqrt(33)/7.

If in Q III, the opp side will be negative, so that the sine of theta is -sqrt(33)/7.

CAN YOU NOW use this info to find tan theta, first for theta in Q II and then for theta in Q III?

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