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Two simple C3 questions

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?
q8.png

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 :s-smilie:.

q9.png

Thanks in advance :smile:.
Reply 1
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
Reply 2
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.
Reply 3
sin^y = 4x^2
Its a C2 trig identity from there. You are simply trying to eliminate y from your expression.
Reply 4
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 :smile:.

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