If tanx=5/12 then what is sinx/2?

Answer 1

Make a triangle.
By Pythagoras
r^2 = 5^2 + 12^2
r = 13

so sinx = 5/13 and cosx = 12/13

I will assume you meant sin(x/2)

using cosx = 1 - 2sin^2 (x/2)
12/13 = 1-2sin^2 (x/2)
2sin^2 (x/2) = 1/13
sin^2 (x/2) = 1/26
sin (x/2) = 1/√26 or √26/26