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  1. #1
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    trigonometry equationsss =(

    hii guyz, i would REALLY like some help for these trig equation questions
    thank you sooo much if you can helpp me !

    if secx - tanx = 3/5, show that sinx = 8/17

    if tanx = t, express sin2x and cos2x in terms of t. Find the values for t for which

    (k+1)sin2x + (k-1)cos2x = k+1

    thankyouuuu againn !!
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  2. #2
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    Quote Originally Posted by iiharthero View Post
    hii guyz, i would REALLY like some help for these trig equation questions
    thank you sooo much if you can helpp me !

    if secx - tanx = 3/5, show that sinx = 8/17
    Hi

    \sec x - \tan x = \frac35 \implies \frac{1-\sin x}{\cos x} = \frac 35 \implies 5(1-\sin x) = 3 \cos x

    Square both sides and substitute cos²x with 1-sin²x to find a quadratic in sin x, one of the solutions being "impossible" the other one is the good one
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  3. #3
    MHF Contributor red_dog's Avatar
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    Quote Originally Posted by iiharthero View Post

    if tanx = t, express sin2x and cos2x in terms of t. Find the values for t for which

    (k+1)sin2x + (k-1)cos2x = k+1
    \sin 2x=\frac{2\tan x}{1+\tan^2x}, \ \cos 2x=\frac{1-\tan^2x}{1+\tan^x}
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