SOLUTION: If A and B are two angles in Quadrant 2 such that tan A=-1/2 and tan B=-2/3, find cos(A+B). Thank you so much for all of your help!!!! God Bless!!!!!

Algebra ->  Trigonometry-basics -> SOLUTION: If A and B are two angles in Quadrant 2 such that tan A=-1/2 and tan B=-2/3, find cos(A+B). Thank you so much for all of your help!!!! God Bless!!!!!      Log On


   

Question 391236: If A and B are two angles in Quadrant 2 such that tan A=-1/2 and tan B=-2/3, find cos(A+B).
Thank you so much for all of your help!!!!
God Bless!!!!!
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
tan A = -1/2 ==> 1+%2B+%28tan+A%29%5E2++=+1%2B1%2F4+=+5%2F4+=+%28sec+A%29%5E2+ ==> sec+A+=+-sqrt%285%29%2F2 ==> cos+A+=+-2%2Fsqrt%285%29.
tan B = -2/3 ==> 1+%2B+%28tan+B%29%5E2++=+1%2B4%2F9+=+13%2F9+=+%28sec+B%29%5E2+ ==> sec+B+=+-sqrt%2813%29%2F3 ==> cos+B+=+-3%2Fsqrt%2813%29.
Now