SOLUTION: Hello I really need help for this question,so if you guys can help I will be really appreciated. The question is I have to use a double-angle identity to find the exact value of co

Algebra ->  Trigonometry-basics -> SOLUTION: Hello I really need help for this question,so if you guys can help I will be really appreciated. The question is I have to use a double-angle identity to find the exact value of co      Log On


   

Question 967167: Hello I really need help for this question,so if you guys can help I will be really appreciated. The question is I have to use a double-angle identity to find the exact value of cos x =12/13 and it said 0 degree I don't get how this thing (0
Answer by tenkun(12) About Me  (Show Source):
You can put this solution on YOUR website!
cos x =12/13
Sin^2x= 1- cos^2x
. = 1- 144/169
= 169/169 -144/169
= 25/169
Sin x= √25/169
= 5/13
Sin 2x = 2*sin x * cos x
= 2 * 5/13 * 12/13
= 120/169