CIE A Level Maths: Pure 1复习笔记3.3.2 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