Question 1077273
Given that cos(t) = -15/17, we know the adjacent side is 15 (QII) and the hypotenuse is 17.
Let the opposite side by x.  Then sin(t) = x/17
From the Pythagorean theorem we know that x^2 = 17^2 - 15^2
We can make use of the identity, cos(2t) = cos^2(t) - sin^2(t)
sin^2(t) = x^2/17^2 = (17^2-15^2)/17^2 = 1 - (15/17)^2
Therefore, cos(2t) = (-15/17)^2 - [1-(15/17)^2] = (450-289)/289  = 161/289
Ans: b