SOLUTION: find the cosine of the angle formed with the coordinates (-6, 7) located in standard position

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Question 197567: find the cosine of the angle formed with the coordinates (-6, 7) located in standard position
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
find the cosine of the angle formed with the coordinates (-6, 7) located in standard position

Plot the point (-6,7)



Draw the radius vector, r, from the origin (0,0) to the point (-6,7). 



Indicate the angle.  I'll call it alpha.



Draw a vertical line perpendicular down to the x-axis, and
label it y=7.



Draw a horizontal line from the origin to the bottom of
that line, completing a right triangle.  Label it x=-6



Now we find the length of r by the Pythagorean theorem:

r%5E2=x%5E2%2By%5E2
r%5E2=%28-6%29%5E2%2B%287%29%5E2
r%5E2=36%2B49
r%5E2=85
r=sqrt%2885%29

So we put r=sqrt%2885%29 for r: 



Now since

cos%28alpha%29=x%2Fr

cos%28alpha%29=%28-6%29%2Fsqrt%2885%29

cos%28alpha%29=-6%2Fsqrt%2885%29

Edwin