Prove each trig identity below. (1) cos(pi/2 + x) = -sin(x) (2) cos(A + B) + cos(A - B) = 2 cosA cos B
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Originally Posted by magentarita Prove each trig identity below. (1) cos(pi/2 + x) = -sin(x) (2) cos(A + B) + cos(A - B) = 2 cosA cos B (1) -> use this formula : , and remember these two values : (2) -> use the formula above and this formula : (this is because cosine is an even function and sine an odd function) Then, add up
For both questions, prove the LHS. I want to see your attempt and people will point out any mistakes, if any.
Originally Posted by Moo (1) -> use this formula : , and remember these two values : (2) -> use the formula above and this formula : (this is because cosine is an even function and sine an odd function) Then, add up Thanks for the tips.
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