Pure: Trigonometry

The sine rule states that the ratio of the length of a side of a triangle to the sine of its opposite angle is constant for all three sides. Therefore, a/sin A equals b/sin B. Distractors like A are incorrect because they use the cosine function instead of sine, which violates this fundamental trigonometric relationship.

This expression represents the fundamental Pythagorean trigonometric identity, which always equals 1 for any angle theta. Option D is incorrect because tangent theta is defined as the ratio of sine to cosine, rather than the sum of their squares.

This expression represents the fundamental Pythagorean trigonometric identity, which always equals 1 for any angle theta. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.

• !Option D is incorrect because tangent theta is defined as the ratio of sine to cosine, rather than the sum of their squares.
• !Option A is incorrect because 30 degrees is equivalent to pi divided by 6, which is a common confusion when associating the number 3 with the angle.
• !Distractors like A are incorrect because they use the cosine function instead of sine, which violates this fundamental trigonometric relationship.

Answer each from memory — you'll see instantly whether you're right and why.

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