**Trigonometry: Addition Formulas**

**Sol 1**

.

**Sol 2**

.

**Sol 3**

.

**Sol 4**
.

**Sol 5**
.

**Sol 6**

.

**Sol 7**
.

**Sol 8** Let be the angle between the first line and the positive
x-axis, and let be the angle between the second line and the positive
x-axis. Then the angle between the two lines is given by
, and
and
; so

, so .

Return to the Problems for this
Topic.

Return to Precalculus Home Page.