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# Edexcel Maths trig q help watch

1. Show that:

sinx +sin3x + sin5x +sin 7x = (16sinx )(cos^2x)((cos^2(2x))
2. If you don't want to churn through the algebra using the addition and double angle formulae for sine and cosine. Why don't you try rewriting what you have as:

sin(x) + sin(3x) + sin(5x) + sin(7x) = Im [ e^ix + e^3ix + e^5ix + e^7ix ]

and noting that it is a geometric series!
3. (Original post by frankabagnale)
Show that:

sinx +sin3x + sin5x +sin 7x = (16sinx )(cos^2x)((cos^2(2x))
What have you tried?

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