Given that cos a 12/3 and a is an angle in Quadrant II and that sin Beta = 3/5 is an angle in Quadrant I. Determine
a) cos (a + Beta)
b) sin (Beta - a)
Incorrect conditions. "Given that cos a 12/3..." What does it mean? If that cos a = 12/3, then it's impossible, because cos (in real analysis) is bounded function and its value are in [-1;1], but 12/3 = 4, which is bigger than 1.