Question

if if sin theta + sin square theta is equal to 1 show that cos square theta + cos 4 theta is equal to 1​

Answer 1

hey here is your answer

Answer 2

sin∅ + sin²∅ = 1 (given)

Also, cos²∅ + sin²∅ = 1 (identity)

Comparing,

=> sin∅ = cos²∅

Now,

cos²∅+cos⁴∅ {LHS}

= sin∅ + sin²∅

= 1 (given) {RHS}

LHS=RHS

Hence proved.