Question

(cos5α+5cos3α+10cosα)/cos⁵α=

Answer 1

$frac{cos5a+5cos3a+10cosa}{cos^5a}=\ cos5a=16cos^5a-20cos^3a+5cosa\ cos3a=4cos^3a-3cosa\\ frac{16cos^5a-20cos^3a+5cosa+20cos^3a-15cosa+10cosa}{cos^5a}=\\ frac{16cos^5a}{cos^5a}=16$