Question

Show that none of the following is an identity: 

`sin^2 theta + sin  theta =2`

Answer 1

`sin^2 theta + sin  theta =2`

LHS = `sin^2 theta + sin theta`

        =`1- cos^2 theta + sin theta `

        =`1- ( cos ^2 theta - sin theta )`

 Since LHS ≠ RHS, this is not an identity.