**TRIGONOMETRY FOR STATICS**

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**PART 3:**

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**Values of
Trigonometric Functions at Specific Angles:**

**For 0 ^{o} and 90^{o}:**
These functions are limiting values that can be observed from the drawing. As
side y approaches 0 (zero), the

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**For 30 ^{o} and 60^{o}_{:}**

**For 45 ^{o}_{:}**

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Basic identities:

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**Half-angles:**

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Identities in terms of tan (q/2):

where

**Curves of
Sine, Cosine, and Tangent:**

**Sine function:**

The sine function is an odd function since

**Cosine function:**

The cosine function is an even function since

**Tangent function:**

The tangent function is an odd function since

Note that

as

**Approximation
of Trigonometric Functions at Small Angles:**

As a close approximation, when an angle(expressed in radians) is very small, we may use the following approximations

- replace with
- replace with
- replace with unity (i.e., )