Question

Check my work, error somewhere...

Answer 1

Using the formula cos 2A= cos^2A-sin^2A =
(-5/17)^2 - 9-8/17)^2
25/289 - 64/289 = -39/289

Answer 2

\(\color{blue}{\displaystyle \tan(2A)=\frac{\sin(2A)}{\cos(2A)}=\frac{2\sin(A)\cos(A)}{2(\cos A)^2-1} }\)

Answer 3

you know Sin(A)=-8/17 and Cos(A)=-15/17.

Answer 4

since tan 2A = sin 2A/cos 2A
sin 2A in this case is 240/289 multiplying that by -39/289 = -240/39

Answer 5

240/161 is what get.

Answer 6

Oh, I'm so funny. There was an error in my math. Thanks! @SolomonZelman

Answer 7

Np, it happens to any of us:)