Mathematics (AS)·Trigonometry · NSSCAS 1.6.2
Exact values & inverse trig notation
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Some angles are so special that we never need a calculator for them. In this lesson you will build two magic triangles with your own pen and read off the exact sine, cosine and tangent of 30, 45 and 60 degrees. Then we stretch to related angles like cos 150 degrees using the CAST diagram, switch to radians, and finally decode the inverse notation sin⁻¹x, cos⁻¹x and tan⁻¹x with their principal values. By the end, exact-value questions become free marks.
What you'll learn in this lesson
By the end you should be able to (NSSCAS Mathematics (AS) 1.6.2):
- Use the exact values of the sine, cosine and tangent of 30°, 45°, 60° and related angles, e.g. cos 150° = −½√3.
- Use the notations sin⁻¹x, cos⁻¹x, tan⁻¹x to denote the principal values of the inverse trigonometric relations.
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