Question

If sin¤ +sin²¤=1 then find the value of cos²+cos^4

Answer 1

 cos2 theta+cos4 theta

=1-sin2 theta+cos2 theta*cos2theta

=sin theta+(1-sin2 theta)(1-sin2 theta)

=sin theta+sin theta*sin theta

=sin theta+sin2 theta

= 1

Answer 2

Answer:

Given

sinA+sin²A=1

=>sinA+(1-cos²A)=1

[1-cos²A=sin²A]

=>sinA-cos²A=1-1

=>sinA=cos²A

Now

cos²A+cos⁴A

=cos²A+(sinA)²

=cos²A+sin²A

=cos²A+1-cos²A

=1