For general solutions

We must learn

**
For sin x = sin y,
**

x = nπ + (–1)
^{
n
}
y, where n ∈
**
Z
**

**
For
**
**
cos x
**
**
=
**
**
cos y
**
**
,
**

x = 2nπ ± y, where n ∈
**
Z
**

**
For
**
**
tan x
**
**
=
**
**
tan
**
**
y,
**

x = nπ + y, where n ∈
**
Z
**

Note: Here n ∈Zmeans n is an integer