Are` phi and {phi}` same?`n{phi}`?

Eliminate theta and phi sintheta+sinphi=a , costheta+cosphi=b , theta-phi =a

What is the difference between phi and {phi}

State true / false: phi , {phi} ,0,{0} are all different from one another.

Eliminate theta and phi costheta +sintheta=a , sintheta*costheta =b

Eliminate theta and phi x costheta+y sintheta=a , y costheta-x sintheta=b

If cos^2theta- sin^2theta= tan^2 phi , then prove that cos^2phi – sin^2phi= tan^2theta

Eliminate theta and phi x sintheta=a , y tantheta=b

Eliminate theta and phi sintheta +costheta =x , tantheta +cottheta=y

Show that the average power dissipated depends not only on only on the voltage and current, but also on the cosine of the phase angle phi between them.

Eliminate theta and phi sintheta+costheta=a , sin^3theta+cos^3theta=b