A-to-Z

Types of trigonometric scales

Trigonometric scales on slide rules are presented in different ways. The following table shows the main variants.

Type Variant Notes
Scales on stock
Scales on slide Front face
Reverse face - marks on back of stock
Reverse face - slide has to be reversed
 

Same as with scale on front face of slide.

Differential trig scales Patented - only on Thornton rules.

The next table looks at the suitability of these main configurations for three different types of calculations:

The following assume use of the trig scales with the C and D scales. On some rules it may be necessary to modify the instructions slightly for use with A and B scales.

Arrangement Multiplying by function Dividing by function Combined multiplication and division
Trig scales on stock Cursor to  36.9 on S scale.
10 on B scale to Cursor.
Read answer, 3, on D scale against 5 on  C scale.
Cursor to angle 36.9 on S scale.
3 on C scale to cursor.
Read answer, 5, on C scale against 10 on D scale.
Cursor to 45 on S scale.
3 on C scale to cursor.
Cursor to 30 on S scale.
Read answer, 2.12, on C scale.
Trig scales on slide front face 10 on C scale to 5 on D scale.
Cursor to 36.9 on S scale.
Read answer, 3, on D scale against cursor.
Cursor to 3 on D scale.
36.9 on S scale to cursor.
Read answer, 5, against 10 on D scale.
Cursor to 3 on D scale
45 on S scale to cursor
Cursor to 30 on S scale
Read answer, 2.12, on D scale.
Trig scales on reverse with marker on stock. 36.9 on S scale to mark on back
Read answer, 3 on C scale, against 5 on D scale.
36.9 on S scale to mark on back
Read answer, 5 on D scale, against 3 on C scale.
45.0 on S scale to mark on back
Cursor to 3 on C scale.
30 on S scale to mark on back.
Read answer, 2.12, on C scale.
Differential trig scales. Cursor to 36.9 on D scale.
36.9 on Sd scale to cursor.
Read answer, 3, on D scale against 5 on C scale.
Cursor to 36.9 on D scale.
36.9 on Sd scale to cursor.
Read answer, 5, on C scale against 3 on D scale.
Set 45 on C scale against 30 on D scale.
Cursor to 45 on Sd scale.
30 on Sd scale to cursor.
Read answer, 2.12, on D scale against 3 on D scale.