**There are 2 exercises on this page:**

**For this first exercise we will determine the CHORD (line “BC”) of an arc if we know the RISE “AD” and the RADIUS.**

Our radius **Radius** will be **96 inches** and the **Rise** (line **“AD”**) will be **24 inches**.

**96 – 24 = 72** Now **96 ² – 72 ² = 4032.** Now **√***(**square-root)* you get **63.5″**

Now **x 2 = 127 inches.**

The **CHORD** of this arc is **127 inches**.

**In Short:**

**Radius – Rise = X Radius² – X² = ___ ****√ ___ x 2 = CHORD**

This exercise is good for all angles of less than 180 degrees of arc.

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**In this second exercise, we will determine the CHORD of an arc, if we know the RADIUS and the ARC LENGTH.**

**This exercise is useful when Rolling Rings of less than 180 degrees of arc.**

Our **Radius** will be **120”** and the **Arc Length** will be 288**”.**

Punch in **120” x **** = **you get **376**.99

Now **376.99 ÷**** 288 = **you get **1.309.**

Now hit the **1/X** key, you get **.7639**.

Now **x 180 =** you get **137.51 **Now divide by **2** = **68.755**

Punch **SIN **you get **.932** now **x 120”** = **111.845**

Now **111.845 x 2 =223.69” **

**Your CHORD is 223.69”**

** ****In Short:**

**Radius x **** = ____ ****÷**** **** Arc Length = ____ 1/X x 180 = Angle**

**÷ 2 = ____ SIN ____ x Radius = ____ x 2 = CHORD**