Question

Упростите выражения: (1+tg^2 a) * cos^2 a - sin^2 a

Answer 1

$(tan^2(a)+1)*cos^2(a)-sin^2(a)$
$sec^2(a)*cos^2(a)-sin^2(a)$
$( \frac{1}{cos(a)} )^2*cos^2(a)-sin^2(a)$
$\frac{1^2}{cos^2(a)} *cos^2(a)-sin^2(a)$
$\frac{1}{cos^2(a)} *cos^2(a)-sin^2(a)$
$\frac{1}{1}* \frac{1}{1} -sin^2(a)$
$\frac{1}{1}-sin^2(a)$
$1-sin^2(a)$
$cos^2(a)$