How do you solve these ?

a) Prove that for all values of x : (cos^4)x - (sin^4)x = (cos^2)x - (sin^2)x

b) Given that 5(cos^2)x + 2(sin^2)x = 4, show that (tan^2)x = 1/2

Urgent help needed. Thank you very much ! :)

by kalpm

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