SOLUTION: If sin α = 4/5 and cos β = -5/13 for α in Quadrant I and β in Quadrant II, find cos(α - β).

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Question 1117290: If sin α = 4/5 and cos β = -5/13 for α in Quadrant I and β in Quadrant II, find cos(α - β).
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!




and



But for

Hence

Similarly, and I leave the arithmetic to you:



Therefore:



The rest is just arithmetic. Mind your signs.

John

My calculator said it, I believe it, that settles it