Question

V2 Find the exact value of cos (a - b) if sin a = 2 and cos p= - 3 with a in quadrant l and in quadrant II. cos (a - b) = 1 (Simplify your answer, including any radicals. Use integers or fractions for any numbers in the expression.)

Answer 1

2nd quadrant Ist quadrant Only sino and coco All trigonometric functions are positive are positive Only coso and seco are positive Only tano and coto positive are 3rd quadrant 4th quadrant

are positive x is in quadrant I =) All trigonometric identities =) cosa is positive Using, sina+cos d=1 cos²x = 1-sin²a cosa = 1-sind z) cosa 2 2 =) cosa= 2 4 =) cosa= alt, - cosa = Lol 2 ß is in quadrant I =) sinß is positive Using. sin?ß + cos² ß=1 -) sin'B - 1-Cos =) sinß=√1-cosß =) sinß- J-1 3 sinß- 1+ = sinß = √3 1+1 2 2

cosla-B1 = cosa cosß+sindsinß -- ()4}+(?)(5 - -2 4 t Lift = 56-52 4
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