Question

1−sec^2  /  ^ 2−1 equals:

a) −sec2
b) tan4
c) − tan4
d) 1.​

Answer 1

Step-by-step explanation:

secx+sec2x=1

⇒secx=1−sec2x=tan2x

⇒sec2x=tan4x

⇒1+tan2x=tan4x

(1+tan2x)2=(tan4x)2

1+tan4x+2tan2x=tan8x

∴tan8x−tan4x−2tan2x+1

=1+tan4x+2tan2x−tan4x−2tan2x+1

=2