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Two simple C3 questions

1. Can someone explain these two questions to me as im not sure how they get to the answer.

On question 8, when they say find the range, is it basically what value of x is needed to make f(x) positive?

On question 9c im not sure how they get to the answer. I understand the first part where they use the reciprocal from part bii but they last 3 parts i'm not sure if its random or intended .

2. They are not easy if you can't answer them though right?

1st one: Draw the graph, its a basic stretch followed by a translation. The range previously would have been f(x)>0
Therefore what will happen now?

2nd one: cos^2y + sin^2y = 1
siny = 2x
Play with it from there
3. (Original post by kozo)
They are not easy if you can't answer them though right?

1st one: Draw the graph, its a basic stretch followed by a translation. The range previously would have been f(x)>0
Therefore what will happen now?

2nd one: cos^2y + sin^2y = 1
siny = 2x
Play with it from there
Thanks for your reply, i understand the first one, i'm just asking to confirm and the second one i'm still not entirely sure how to do.
4. sin^y = 4x^2
Its a C2 trig identity from there. You are simply trying to eliminate y from your expression.
5. (Original post by kozo)
sin^y = 4x^2
Its a C2 trig identity from there. You are simply trying to eliminate y from your expression.
Ok thank you i understand it now .

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