Find the exact value of the expression. 6) cos 20° cos 40° - sin 20° sin 40° A) 1 943 Use the given information to find the exact value of the expression. 7) sin a=- a lies in quadrant 1, and cos ß-2 ß lies in quadrant I A). 132 B) 468 493 C) 155 493 493 1|2 D)√√3 Find cos (a + B). D) 475 493 7)