SOLUTION: find the exact value of cos(u-v) given that sin u = -(12/13) and cos v = -(3/5) and both u and v are in QIII

Question 1085621: find the exact value of cos(u-v) given that sin u = -(12/13) and cos v = -(3/5) and both u and v are in QIII
Answer by ikleyn(52798) (Show Source): You can put this solution on YOUR website!
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1.  Since sin(u) = , cos(u) =  =  =  =  = +/- .

   Since "u" is in Q3, cos(u) is negative, and we have cos(u) = .


2.  Similarly, sin(v) =  = .


3.  Now, cos(u-v) = cos(u)*cos(v) + sin(u)*sin(v) =  =  = .


Answer. .

Solved.

To see more solved similar problems on calculating trig functions look into the lessons
    - Calculating trigonometric functions of angles
    - Advanced problems on calculating trigonometric functions of angles
in this site.

Also, you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Trigonometry: Solved problems".

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