Objective:

To find inverse sines and tangents.

General:

• By reversing the techniques of finding the trigonometric ratios of angles, given the ratio, we can find the angle.
• The inverse notation may be written as:

arc<ratio>(value) or <ratio>^-1(value)

e.g. arcsin(0.5) or sin^-1(0.5)

 Method:

• Move the cursor to the ratio value on the C (or CI) scales.
• Read the angle on the relevant S or T (or ST) scale.

 

Example 1:  Calculate sin^-1(0.655)

• Move the cursor to C0.655
• Read the result S40.9

 

Example 2: Calculate tan^-1(2.46)  (Ratios greater than 1 are found on the CI scale, since the angles are greater than 45°.)

• Move the cursor to CI2.46
• Read the result T22.1
• Answer: 67.9°

 

Example 3:  Calculate sin^-1(0.012) (Values less than about 0.1 require the use of the ST scale.)

• Move the cursor to C0.012
• Read the result ST0.69