Hey there :)
- tan²x + sec²x = 1 or 1 + tan²x = sec²x
sin²x + cos²x = 1
Divide the whole by cos²x
[tex] \frac{sin^2x}{cos^2x} + \frac{cos^2x}{cos^2x} = \frac{1}{cos^2x} [/tex]
[tex] \frac{sinx}{cosx} = tanx[/tex] so [tex] \frac{sin^2x}{cos^2x} = tan^2x[/tex]
and
[tex] \frac{1}{cosx} = secx [/tex] so [tex] \frac{1}{cos^2x} = sec^2x[/tex]
Therefore,
tan²x + 1 = sec²x
Take tan²x to the other side {You will have the same answer}
1 = - tan²x = sec²x or sec²x - tanx = 1
