Question

A expressao (secx-tgx) . (secx+tgx) equivale a :
A) -2
B)-1
C)0
D)1
E) 2

Answer 1

(secx-tgx).(secx+tgx)
$sec^{2}x - tg ^{2} x$
$\frac{1}{cos^{2}x } - \frac{sen^2x}{cos^2x}$
$\frac{cos^2x+sen^2x}{cos^{2}x } - \frac{sen^2x}{cos^2x}$
$\frac{cos^2x+sen^2x-sen^2x}{cos^{2}x }$
$\frac{cos^2x}{cos^{2}x }$
=1