Resposta:
[tex]\textsf{Leia abaixo}[/tex]
Explicação passo a passo:
[tex]\mathsf{\left(\dfrac{1}{sen^2\:x}\left) \times \left(\dfrac{sen^2\:x}{sen^2\:x - 1}\right)}[/tex]
[tex]\mathsf{\left(\dfrac{1}{sen^2\:x}\right) \times \left(\dfrac{sen^2\:x}{1 - cos^2\:x - 1}\right)}[/tex]
[tex]\mathsf{\left(\dfrac{1}{sen^2\:x}\right) \times -\left(\dfrac{sen^2\:x}{cos^2\:x}\right)}[/tex]
[tex]\mathsf{-\left(\dfrac{1}{cos^2\:x}\right)}[/tex]
[tex]\mathsf{-\left(\dfrac{1}{cos\:x}\right)^2}[/tex]
[tex]\boxed{\boxed{\mathsf{\dfrac{1}{sen^2\:x} \times \dfrac{sen^2\:x}{sen^2\:x - 1} = -sec^2\:x}}}[/tex]
