SOLUTION: Given: A lies in Quadrant III and B lies in Quadrant II,
m1212.
Find the exact value of cos(A - B). SinA= -8/17 CosB= -4/5
Algebra ->
Trigonometry-basics
-> SOLUTION: Given: A lies in Quadrant III and B lies in Quadrant II,
m1212.
Find the exact value of cos(A - B). SinA= -8/17 CosB= -4/5
Log On
Question 746467: Given: A lies in Quadrant III and B lies in Quadrant II,
m1212.
Find the exact value of cos(A - B). SinA= -8/17 CosB= -4/5 Found 2 solutions by lwsshak3, solver91311:Answer by lwsshak3(11628) (Show Source):
You can put this solution on YOUR website! Given: A lies in Quadrant III and B lies in Quadrant II,
m1212.
Find the exact value of cos(A - B). SinA= -8/17 CosB= -4/5
***
sinA=-8/17
..
cosB= -4/5
sinB=3/5 (from 3-4-5 right triangle)
..
cos(A-B)=cosAcosB+sinAsinB=(-15/17)(-4/5)+(-8/17)(3/5)=60/85-24/85=36/85
..
Check: (with calculator)
sinA=-8/17
A≈208.07º
cosB=-4/5
B≈143.13º
A-B≈64.94º
cos(A-B)≈cos(64.94º)≈0.4235..
Exact ans=36/85≈0.4235..
(
