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Express cos5x in terms of increasing powers of cosx

De Moivre's theorem: (cos5x + isin5x) = (cosx + isinx)⁵ To get cos5x we will need to expand (cosx + isinx)⁵ and then take the real parts. Binomial expansion: (cosx + isinx)⁵

Answered by Chris S. • Further Mathematics tutor

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Show, using the focus-directrix property for an ellipse, that PS +PS'=2a where P is a point on the ellipse and S and S' are the two foci.

The focus diretrix property for an ellipse is PS/PD=e. Now this is also the case for the other directrix and focus, so PS'/PD'=e. Now we can rearrange these equations to find a formula for PS +PS', PS +PS...

Answered by Daniel L. • Further Mathematics tutor

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How do you deal with 3 simultaneous equations? (Struggling with Q7 of AQA specimen paper 1)

If you need to solve them, then you just plug your way through the algebra to get to the answer.

In this question (Q7) you need to find the value of a constant such that there is no solution to the...

Answered by Joanna W. • Further Mathematics tutor

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Given that p≥ -1 , prove by induction that, for all integers n≥1 , (1+p)^k ≥ 1+k*p.

First of all, we need to show that the statement is true for the base case n=1. For this case the expression becomes: 1+p≥1+p, which is clearly true as both sides are equal and hence solve the inequality....

Answered by Ellen B. • Further Mathematics tutor

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It is given that f(x) = 2sinhx+3coshx. Show that the curve y = f(x) has a stationary point at x =-½ ln(5) and find the value of y at this point. Solve the equation f(x) = 5, giving your answers exactly

1.Differentiating: f'(x)= 2cosh(x)+3sinh(x) At a stationary point, we know f'(x)=0. Therefore 2cosh(x)+3sinh(x)=0. (easy to forget that unlike nromal trig there is no change in sign) Rearranging gives tan...

Answered by Simon B. • Further Mathematics tutor

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