The power dissipated in an electric circuit is given by the expression P RI2 where R is the resistance of the circuit and I is the current through the circuit For a sinusoidal alternating current the current might be represented by the relation I A sin 27ft where A is the amplitude f is the frequency and t is time Write an expression for P involving the sine function and use a fundamental identity to write P in terms of the cosine function O P RA sin 2nft P RA cos 2nft OP RA sin 2ruft P RA RA cos 2 ft P RA sin 2 ft P 1 RA cos 2nft OP RA sin 2ruft P RA RA cos 2nft