Question

Evaluate cot870°.
1. - sqrt3
2. -1/sqrt3
3. 1/sqrt3
4. sqrt3

Answer 1

use math-way

Explanation:

= - square root of 3

Answer 2

`-√(3)`

EXPLANATION

The given angle is 870°.

870°-360°-360°=150°

This means that:

870° is coterminal with 150°, hence its terminal side is in the second quadrant.

It makes an acute angle of 30° with the x-axis.

Note that cotangent is negative in the second quadrant,

Hence,

`\cot(870 \degree) = \cot(150 \degree) = - \cot(30 \degree) = - (1)/( \tan(30 \degree) ) = - √(3)`

The first option is correct.