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Solving trig questions

http://www.examsolutions.net/exampapers/edexcel-c3-january-2010/

For q8 of this paper, can someone explain why cot2x is changed into cos2x/sin2x
Why doesn't it work by changing it to 1/tan2x =0 ??

Thanks
Original post by coconut64
http://www.examsolutions.net/exampapers/edexcel-c3-january-2010/

For q8 of this paper, can someone explain why cot2x is changed into cos2x/sin2x
Why doesn't it work by changing it to 1/tan2x =0 ??

Thanks


Because 1 over something that varies will NEVER equal 0 therefore you cannot use that form. Tan is made up from cosine and sine at its base therefore you should ALWAYS decompose down to those 2 in these types of questions.
Multiply across by tan2x. You get an undefined equation.
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coconut64
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16
That makes sense now, thanks guys

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