Question

(Cos⁴x-sin⁴x)÷cos²x=1-tan²x

Answer 1

(Cos⁴x-sin⁴x)÷cos²x

(sin^2x + cos^2x)(sin^2x - cos^2x)/cos^2x

(sin^2x - cos^2x)/cos^2x

1-tan²x