SOLUTION: If cos x= -15/17 with x in quadrant III, find the exact value of sin 2x and the quadrant of 2x

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Question 1161413: If cos x= -15/17 with x in quadrant III, find the exact value of sin 2x and the quadrant of 2x
Found 2 solutions by MathLover1, MathTherapy:
Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!
If with in quadrant III, find the exact value of and the quadrant of
given:

find:

use identity:
......substitute cos


use to find sin




=±

In Quadrant III, sine and cosine are negative:

then



° -> In Quadrant


Answer by MathTherapy(10555)   (Show Source): You can put this solution on YOUR website!

If cos x= -15/17 with x in quadrant III, find the exact value of sin 2x and the quadrant of 2x
You may be able to recognize this TRIG function as an 8-15-17 PYTHAG. TRIPLE.

We have: 

As x is in QIII, we get: y = O = - 8, and so, 





Can you now tell which quadrant 2x lies in? 

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