Well, you did make an effort, and it was pretty close. But did you read my response?
Did you read the help for tand and cosd? Why not? There was a reason I wrote that hint. They are different from tan and cos. tan and cos work in radians. But you seem to be using DEGREES. So you NEED to use cosd and tand.
Next, you MULTIPLIED by cos(30). While you may think that
should yield 1/6 as a result, it does not. If you want to divide by the product of two numbers, you need them in parens. So something like this