Question

How do you solve `-cosx=1+2cos(x-pi)`?

Answer 1

`S={2pin}`

Explanation:

`-cosx =1+2cos(x-pi)`-> use formula `cos (A-B)=cosAcosB+sinAsinB`

`-cosx=1+2(cosxcospi+sinxsinpi)`

`-cosx=1+2(cosx*-1+sinx *0)`

`-cosx=1-2cosx`

`-cosx + 2cos x =1`

`cos x = 1`

`x=cos^-1 (1)`

`x=0+2pin = 2pin`