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Prove-that-1-tan-3-1-tan-3-1-2sin-2-




Question Number 93571 by prince 5 last updated on 13/May/20
Prove that ((1−tan^3 θ)/(1+tan^3 θ)) =1−2sin^2 θ
$${Prove}\:{that}\:\frac{\mathrm{1}−{tan}^{\mathrm{3}} \theta}{\mathrm{1}+{tan}^{\mathrm{3}} \theta}\:=\mathrm{1}−\mathrm{2}{sin}^{\mathrm{2}} \theta \\ $$
Commented by mr W last updated on 13/May/20
you can′t prove something which is   false. just test with θ=30°.
$${you}\:{can}'{t}\:{prove}\:{something}\:{which}\:{is}\: \\ $$$${false}.\:{just}\:{test}\:{with}\:\theta=\mathrm{30}°. \\ $$

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