SOLUTION: if cos theta = -8/17 and theta is in quadrant 3, cos 2theta= ? A.161/289 B.-161/289 C.64/289 D.-62/289 and tan 2 theta=? A. -30/217 B-30/161 C.-240/217 D.-240/161

Question 1160411: if cos theta = -8/17 and theta is in quadrant 3,
cos 2theta= ? A.161/289 B.-161/289 C.64/289 D.-62/289
and tan 2 theta=? A. -30/217 B-30/161 C.-240/217 D.-240/161
Found 2 solutions by MathLover1, ikleyn:
Answer by MathLover1(20849)   (Show Source): You can put this solution on YOUR website!

if and theta is in quadrant 3,

answer:
C.

and

if => and
using Pythagorean theorem, we have

and if is in quadrant , in quadrant , , and
....substitute opposite and hypotenuse

then

and

then,

answer:
D.
Answer by ikleyn(52781)   (Show Source): You can put this solution on YOUR website!
.

            Hello, you are, probably, a novice at this forum, so I will provide some instructions to you on writing formulas.

If you want to request , write cos(2*theta), using PARENTHESES.

If you want to request , write cos^2(theta).

If you neglect these rules, nobody will understand you, and your time (as well as the tutors' time) will be spent for NOTHING.

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