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    https://imgur.com/a/3MX2l

    i need help with the question in this link
    i dont understand part b and c
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    Idk which bit of b and c you specified so I'll just explain each bit.


    iii) and c

    4tan4xsin4x = 15

    Let's think of this as tan x, and sin x, and find those roots

    express tan x as sin x/cos x, multiply through by sin x to get 4sin^2x/cos x = 15, multiply through by cos x and use the sin^2 + cos^2 = 1 identity specific to this situation, you should obtain a disguised quadratic in cos x, the same quadratic you solved, the only thing left now is to divide your roots by 4, as this is 4x.
 
 
 

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