Please format code as such, using fenced code block, see How to post in the Questions category.
If you mean 10 degrees, you should be able to write 10deg. See Angle Type – Typst Documentation.
I’m guessing the code you need is:
lq.plot(relativedistancexvalue,relativedistancexvalue.map(x=>(1.3*calc.atan((2.5/x) +0.15))+10deg))