Solution; general solution and particular solution

General solution of sinx=tanx

General solution of (tany)dy=dx is

Given the general solution as y = (x^2 + c) e^(-x) of a differential equation, what is the particular solution if y = 0 when x = 1.

General solution of cosx=1 is

Find the principal solution and general solutions : tan theta = (-1)/(sqrt(3))