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

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

To find the value of sin(x/2), we need to use a trigonometric identity. Specifically, we can use the half-angle formula for sine, which states:

sin(x/2) = ±√[(1 - cosx) / 2]

To use this formula, we first need to find the value of cosx. Since we are given that tanx = 5/12, we can use another trigonometric identity:

tanx = sinx / cosx

Rearranging the equation, we have:

cosx = sinx / tanx

Plugging in the given value of tanx = 5/12, we can solve for cosx:

cosx = sinx / (5/12)
cosx = (12/5) * sinx

Now that we have the value of cosx, we can substitute it into the half-angle formula:

sin(x/2) = ±√[(1 - (12/5) * sinx) / 2]

Unfortunately, we do not have enough information to determine the exact value of sin(x/2) since the value of sinx is unknown. However, we can simplify the expression further using the given information if necessary.