Common Trigonometry Mistakes
Example: Solving a trigonometric equation |

Some problems provide the opportunity for more than one mistake. The Goal
Solve the following equation for 0 ≤ x ≤ 2π:
The Mistakes
Find the mistakes:
(Roll the mouse over the math to see a hint in red) (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) Explanations
In the first mistake no use was made of the double angle formula for sine. The student then incorrectly produced tan(2x) from an expression that did not involve cos(2x) and, even if cos(2x) had appeared where cos(x) appears, would have been the reciprocal, namely cot(2x). |

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