Write fractions in simplest form 3.6+{-2.4}

I’m stuck on this i don’t understand.

What basic trigonometric identity would you use to verify that sin x cos x tan x =1-cos^(2)x?

The ksp expression for the system pbcl2(s) pb+2(aq) + 2 cl-(aq) is: [pbc12][pb+2][2cl-] [pb+2][cl-]2 [pb+2][2cl-]2 [pbcl2][pb+2][cl-]2 [pb+2][2cl-]2[pbcl2]