Quandaries
and Queries 

A cyclist is travelling in the direction of 12i+5j at a speed of 39 km/h where i is a unit vector due east and j is a unit vector due north. The wind appears to the cyclist to be blowing with a velocity of (4i+j) km/h. Find, correct to 1 d.p (a) the true speed of the wind and (b) the bearing from which the wind is blowing 

Hi, What the cyclist perceives as the wind is a result of the true velocity of the wind and the cyclist's own velocity. Suppose that the velocity of the wind is
then what the cyclist perceives, 4i + j is the sum of 12i + 5j and ai + bj, that is
Penny 

