Question

ayudaaa porfavor es urgente ayudaaa​

Answer 1

Recuerda:

$\sec(x) = \frac{1}{ \cos(x) }$

$\sin {}^{2} (x) + \cos {}^{2} (x) = 1 \\ \sin {}^{2} (x) = 1 - \cos {}^{2} (x)$

...

$E = ( \sec(x) - \cos(x) ) \cos(x) \\ E = ( \frac{1}{ \cos(x) } - \cos(x) ) \cos(x) \\ E = (\frac{1 - \cos {}^{2} (x) }{ \cos(x) } ) \cos(x) \\ E = 1 - \cos {}^{2} (x) \\ E = \sin {}^{2} (x)$