Take these five relations: \( \sin 2\theta = 2\sin\theta\cos\theta \), \( \cos 3\theta = 4\cos^3\theta - 3\cos\theta \), \( \sin(A + B) = \sin A\cos B + \cos A\sin B \), \( \sin A + \cos B = 1 \) and \( \tan A = \cot B \).
Put the values 0°, 30°, 45°, 60° and 90° for \( \theta \), A and B, one after another.
Each time, work out the left-hand side and the right-hand side separately.
Note whether the two sides are equal for every value you tried.
Discussion
Which of these relations are true for all values of the angles \( \theta \), A and B?
Which relations are true only for some values, and what do those values have in common?
🔐
That's a peek at activity 1 of 1 - sign in for all of them, full length.