Solve the following equation: `costheta+sintheta=cos2theta+ sin2theta`

Explanation

`costheta+sintheta=cos2theta+sin2theta`​


⇒`costheta−cos2theta=sin2theta−sintheta`​


⇒`2sin((theta+2theta)/2)​sin((2theta−theta​)/2)=2cos((2theta+theta)/2)​sin((2theta−theta)/2)​`​


⇒`sin(3theta/2)​=cos(3theta/2)​`​


...