Question

i) express tan 2A in terms of tan A

ii) express
$cot {}^{2} \: a \: in \: terms \: of \: \cos \:$
Φ
iii) express cos 4 Φ in terms of cos Φ

Answer 1

$tan2a = \frac{2 \tan(a) }{1 - {tan}^{2} a}$