Below is a list of 5 identities that can be verified in more than one way. Choose one identity from the list and verify it.

1. cos(x)+cos(y)=2cos(x+y/2)cos(x-y/2)

2. sin(2theta)=2(sintheta*costheta)

3. 1 + tan^2(x) = sec^2(x)

4. sin(x+y)=sin(x)cos(x)=cos(x)sin(y)

5. cos(x/2) = root1+cos(x)/2