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# c3 questions watch

1. hi

I have a few questions and don't know where to start

1) express 2sinx + 4cosx in the form Rsin(x + a)

2) given f(x) = 2x^3 and g(x)=3x + 1

Evaluate fg(-2)
Find g^(-1)x
State the value of gg^(-1)k
2. 1) I'm pretty sure that A = 45

Let me know if that's right, then i'll write out the workig including R.
3. 1) expand Rsin(x+a) by using compound angle formulae.
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the equate coefficients of and

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can you eliminate R to find a? can you eliminate a to find R?

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and

therefore

NB

then rewrite Rsin(x+a) having found R and a....
4. 2)
can you find fg(x)?
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then substitute x=-2 into fg(x)

to find say y=3x+1, make x the subject, and then replace y with x, and x with
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if you dont see what is right away, try figuring it out in the same way you found fg(x).

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Updated: November 11, 2008
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