if tan 8/15 find the value of sin+cos/cos(1-cos

Answer 1

since tanx = 8/15, you have a standard 8-15-17 right triangle, making
sinx = 8/17
cosx = 15/17
Now just plug those values into your somewhat poorly typed expression
(ever hear of parentheses?) (x+y)/(x-y) is not the same as x+y/x-y (PEMDAS)