SOLUTION: use the cosine of a sum and cosine of a difference identities to find cos (s+t) and cos (s-t). sin s = -5/13 and sin t=4/5, s in quadrant 3 and quadrant 1

Question 1154950: use the cosine of a sum and cosine of a difference identities to find cos (s+t) and cos (s-t). sin s = -5/13 and sin t=4/5, s in quadrant 3 and quadrant 1
Answer by greenestamps(13200) (Show Source): You can put this solution on YOUR website!

5-12-13 is a Pythagorean Triple; sin s = -5/13 in quadrant III means cos s is -12/13.

3-4-5 is a Pythagorean Triple; sin t = 4/5 in quadrant I means cos t = 3/5.

Use the values you now have to find cos (s+t) and cos(s-t):

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