Question

Which of the following statements is not true?

Options

• sin 0° = cos 0°

• tan 30° = cot 60°

• sin 30° = cos 60°

• `sin 45^circ = 1/(sec 45^circ)`

Answer 1

sin 0° = cos 0°

Explanation:

(a) sin 0° = 0 while cos 0° = 1, so sin 0° ≠ cos 0°, so (a) is not true.

(b) `tan 30^circ = 1/sqrt(3)` and `cot 60^circ = 1/sqrt(3)`, so (b) is true.

(c) `sin 30^circ = 1/2` and `cos 60^circ = 1/2`, so (c) is true.

(d) `sin 45^circ = sqrt(2)/2` and `sec 45^circ = sqrt(2)`,

So, `1/(sec 45^circ) = 1/sqrt(2) = sqrt(2)/2`, hence (d) is true.