Trigonometry Exact Values (OCR A Level Maths A) : Revision Note

Trigonometry Exact Values

Exact values

• In trigonometry some values of sin, cos and tan are “nice”

• For example sin 30° = ½, tan 45° = 1

• We can find those associated with the angles 30°, 45° and 60° using SOHCAHTOA on isosceles and equilateral triangles

• sin, cos and tan values for 30°, 45° and 60° should be recalled easily

• Memorise either the actual values or how to work them out from the triangle

• sin, cos and tan for 0°, 90°, 180° should also be very familiar

• They can be recalled using the relevant trigonometric graph (see Graphs of Trigonometric Functions)

Exact values and radians

• All of the above applies to radians as well as degrees

• Here is a table of all exact values including radians (see Radian Measure)

How do I find exact values of other angles?

• Exact sin, cos and tan values of multiples of 30°, 45°, 60° can also be found

• This is a combination of recalling the basic values and using the graph