Gym a charges a yearly fee of $100 plus $10 a month.
gym b charges a yearly fee of $50 plus $15 a month.
after how many months is the cost the same?

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