A car travelled 216km at an average speed of 48km/h. On the return journey the average speed increased to 72km/h. Calculate the average speed, in km/h for the whole journey

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