Practicing Success
If $cosec^2θ + cot^2 θ = \frac{5}{3}$, then what is the value of cot2θ ? |
$\frac{1}{\sqrt{3}}$ $-\frac{1}{\sqrt{3}}$ $\frac{2}{\sqrt{3}}$ $-\frac{2}{\sqrt{3}}$ |
$-\frac{1}{\sqrt{3}}$ |
cosec²θ + cot²θ = \(\frac{5}{3}\) ----(1) cosec²θ - cot²θ = 1 ----(2) On subtracting equation 2 from equation 1. 2 cot²θ = \(\frac{5}{3}\) - 1 cot²θ = \(\frac{1}{3}\) cotθ = \(\frac{1}{√3}\) { we know, cot60º = \(\frac{1}{√3}\) } So, θ = 60º Now, cot2θ = cot ( 2 × 60º) = cot 120º = cot ( 180º - 60º ) { cot is negative in 2nd quadrant } = - cot120º = - \(\frac{1}{√3}\)
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