Convert from polar form to rectangular form.
a) (4, 5π/3)
b) r=7/4cosθ+9sinθ
a) x = r·cos(theta) ---> x = 4·cos(5pi/3) = 4·½ = 2
y = r·sin(theta) ---> x = 4·sin(5pi/3) = 4·-sqrt(3)/2 = -2sqrt(3)
+28 
