Suppose aa represents some number of radians where 0<a<π/2, and cos(a)=0.7 and sin(a)=0.72. Determine the values of the following expressions. cos(−a)= 

sin(−a)= 

Hint: it might help to start by drawing a diagram of two angles: one with a measure of a radians, and one with a measure of −a radians.