Find the value of r that will make the equation sin 73 cos ° = r true when 0 90 °< < ° r . explain your answer.

The sine of an angle is equal to the cosine of the complementary angle. 
That is; sin r = cos 90 -r , where r is an acute angle
Therefore; 
sin 73 = cos (90-73)
sin 73 = cos 17
Hence the value of r = 17