pontifexmaximus
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I was wondering if anybody could help me with this proof by induction question. Prove that

(1/2) + cos(x) + cos(2x) + ... + cos(nx) = [sin(n + (1/2))x]/2sin(x/2)

Thanks!
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DFranklin
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As ever:

What have you tried so far?
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davros
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(Original post by pontifexmaximus)
I was wondering if anybody could help me with this proof by induction question. Prove that

(1/2) + cos(x) + cos(2x) + ... + cos(nx) = [sin(n + (1/2))x]/2sin(x/2)

Thanks!
Do you understand the principle of proof by induction?

What is the base case? Can you prove it?

What is the inductive step? How might you prove it using standard trig formulae?
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