Objective:

To find tangents of angles greater than 45° marked on the standard T scale.

General:

• The normal T scale allows finding tangents of angles in the range 5.7° to 45°.
• Tangents of angles over 45° are greater than 1.
• Tangents of larger angles can be found by using the cotangent scale (generally in red) and CI scale.
• If  the T scale is on the slider you may need to flip the slide rule to read the CI scale.
• Mathematically, the following property is used:

Method:

• Move the cursor to (90° - θ°) on the T scale.
• Read the result from the CI scale.

 

Example 1:  Calculate tan 75.4°.

• Move the cursor to T14.6
• Read the result CI3.84

 

Example 2:  Calculate tan 82.6°.

• Move the cursor to T7.4
• Read the result CI7.7

 

Practice Examples:  Calculate

1. tan 47.6° (Ans: 1.095)
2. tan 63.4° (Ans: 2)
3. tan 77.8° (Ans: 4.625)