**In this section, we will determine the RISE using 2 different methods.**

**Here, we will determine the RISE (line “AD”) of an arc if we know the RADIUS and the ARC LENGTH.**

*This exercise is useful for measuring your target curvature when rolling large radii with relatively short arc length.*

Our **Radius** will be **300″** and the **Arc Length** will be **240″**

**300″ x ∏ = 942.4778″**

Now **942.4778″ ÷ 240″ = 3.927 **Now **1/x** you get **.25465**

Now **x 180º = 45.8366º ** Now **45.8366º ÷ 2 = 22.9183º**

Now **COS – 1 = -.07894** Now **x 300″ = 23.6817″**

Your **Rise** is **23.6817″**

**In short:**

**Radius x ∏ = ___ ÷ Arc Length = ___ 1/x ___ x 180 = ___ ÷ 2 = ___ COS – 1 = Rise**

**NOTE:** The negative number here does not matter.

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

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**Here, we will determine the RISE (line “AD”) of an arc if we know the RADIUS and the CHORD.**

Our **Radius ** will be **60 inches** and the C**hord “BC”** will be **96 inches**.

**60 ² – 48 ² = 1296** now **√***(square-root)*. You get **36**.

Now **36″ – 60″ = 24″**.

The **RISE** (line **“AD”**) of this arc is **24 inches**.

**In short:**

**Radius² – Chord/2² = ___ √ – Radius = RISE**

**NOTE:** The negative number here does not matter.

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