Question

докажите торжество а) 1-cos2x/ 1+cos2x =tg^2x

Answer 1

$displaystyle frac{1-cos2x}{1+cos2x}= frac{1-(1-2sin^2x)}{1+(2cos^2x-1)} = frac{1-1+2sin^2x}{1+2cos^2x-1}= frac{2sin^2x}{2cos^2x} =tg^2x$