Baxter, Jackie, Quincy, and Valerie open savings accounts. At the end of each month, all four friends deposit different amounts of money into their savings accounts. of the four, which friend is saving money at a proportional rate?

Which sum or difference identity would you use to verify that cos (180° - q) = -cos q? a.) sin (a -b) = sin a cos b – cos a sin b b.) cos (a -b) = cos a cos b – sin a sin b c.) cos (a -b) = cos a cosb + sin a sin b d.) sin (a + b) = sin a cos b + cos a sin b