SOLUTION: Find the exact value of the trigonometric function given that sin u = 12/13 and cos v = -4/5. (Both u and v are in Quadrant II.) cos(u − v)

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Question 675342: Find the exact value of the trigonometric function given that sin u = 12/13 and cos v = -4/5. (Both u and v are in Quadrant II.)
cos(u − v)
Found 2 solutions by sachi, lynnlo:
Answer by sachi(548) About Me  (Show Source):
You can put this solution on YOUR website!
Both u and v are in Quadrant II
sin u = 12/13 ,so cos u=sqrt((1-(12/13)^2)=-5/13
and cos v = -4/5. so sin v=sqrt((1-(-4/5)^2)=3/5
so cos(u − v)=cos u cos v+sin u sin v=-5/13*-4/5+12/13*3/5=(20+36)/65=56/65
ans

Answer by lynnlo(4176) About Me  (Show Source):
You can put this solution on YOUR website!
if u and v are in the 4th. quadrant
y=-12,and r=13
sin v=y/r=7/25
cosv=x/r=25/25
tanv=y/x=7/24