**Trigonometry: Double-Angle and Half-Angle Formulas**

**Sol A**
.

**Sol 1**
.

**Sol 2**
, so
since
with
and
.

Therefore .

**Sol 3**

.

**Sol 4**

.

**Sol 5**

.

**Sol 6**

.

**Sol 7**
, so

since for . Then

.

**Sol 8**
, so

since for .

Since , , so

.

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Topic.

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Lawrence Marx 2002-07-11