Question

Cot^4a-1 evaluate this question as soon as possible

Answer 1

$\cot^{4} a - 1 \\ \\ ( { \cot }^{2} a + 1)( { \cot }^{2}a - 1) \\ \\ \underline{\csc^{2} a( \cot a + 1 )( \cot a - 1)}$

Formulas used:

${a}^{2} - {b}^{2} = (a + b)(a - b) \\ \\ \\ \csc^{2} \theta - \cot^{2} \theta = 1 \\ \\ \therefore \: \csc^{2} = \cot^{2} + 1$