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C2 maths help

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    Why does (sin 2x) / (cos 2x) = tan 2x . I thought the answer was tan x because the 2s cancel each other out
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    (Original post by man111111)
    Why does (sin 2x) / (cos 2x) = tan 2x . I thought the answer was tan x because the 2s cancel each other out
    The identity is \tan A \equiv \frac{\sin A}{\cos A} and this is true whatever A is. It could be a number like 0.2 or a variable like 2x. In this case A=2x.

    You can only cancel a number/variable from the top and bottom of a fraction if this number is a factor of the whole numerator and the whole denominator.

    2 is not a factor of \sin 2x so you can't cancel it but 2 would be a factor of 2\sin x for example.
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    (Original post by man111111)
    Why does (sin 2x) / (cos 2x) = tan 2x . I thought the answer was tan x because the 2s cancel each other out
    Let y = 2x

    Then we have siny/cosy = tany.

    There is no cancelling out, which is a common misconception at a first glance.

    Please make your thread titles clearer, specifying C2 is very useful and better than a large number of threads but 'C2 trig question' would be better still
 
 
 
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