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Help! Algebra Question involving trig!! watch

    • Thread Starter

    Im stuck on this question which is really annoyin cos i can normally do this sort of question and would appreciate it if anyone can solve it:

    Show that 4cos2x/(sin2x)^2 is identitically equal to (cosecx)^2 - (secx)^2

    It is on a P3 test so please do not use anything above this level othawise I will not understand!! Also if u use ne otha identities please could u quote them in the solution so i will be able to follow it through.

    Thanx to anyone who can help me out.

    (Original post by the_anomaly)
    Show that 4cos2x/(sin2x)^2 is identitically equal to (cosecx)^2 - (secx)^2
    (cosecx)^2 - (secx)^2 = 1/(sinx)^2 - 1/(cosx)^2
    = [(cosx)^2 - (sinx)^2 ] : (sinxcosx)^2
    = cos2x / [(sin2x)/2]^2
    = cos2x / 0.25(sinx2x)^2
    = 4cos2x/(sin2x)^2.
    That's all.
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Updated: August 4, 2004

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