Common Trigonometry Mistakes
Example: Value of a Trigonometric Function

The Goal

Find the exact value of:


The Mistake

Find the mistake:


(Roll the mouse over the math to see a hint in red)

The Correction


(Roll the mouse over the area above to see the correction in blue)

An Explanation

The angle 5π/6 lies in the second quadrant, with reference angle π - 5π/6 = π/6. Sine is positive in the second quadrant, and so sin(5π/6) = +sin(π/6) = 1/2.

You are expected to know the exact values of the trigonometric functions at all the nice angles. Visit Trigonometric Facts to help learn these values.

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