SOLUTION: Given that cos C = -5/13 with C in quadrand II, find tan 2c I tried using tan(2x) = 2tan(x) / (1 - tan(x)2 but i have no idea?

Algebra ->  Trigonometry-basics -> SOLUTION: Given that cos C = -5/13 with C in quadrand II, find tan 2c I tried using tan(2x) = 2tan(x) / (1 - tan(x)2 but i have no idea?      Log On


   



Question 850183: Given that cos C = -5/13 with C in quadrand II, find tan 2c
I tried using tan(2x) = 2tan(x) / (1 - tan(x)2
but i have no idea?

Answer by fcabanski(1391) About Me  (Show Source):
You can put this solution on YOUR website!
cos is adjacent/hypotenuse. So the adjacent side to the angle (one of the legs) is 5. Since this is quadrant II, it's -5. The hypotenuse is 13. You can find the other leg (opposite side) using the Pythagorean theorem a%5E2+%2B+b%5E2+=+h%5E2 where a and b are legs and h is the hypotenuse. This can be rearranged as


tan2c+=+2%2A%28-12%2F5%29+%2F+%281-%28-12%2F5%29%5E2%29


tan2c = -24/5 / (1-144/25) = -24/5 / (-119/25) = -24/5 * -25/119 = 120/119 = approximately 1.008