Question

Determine the sign of cos pi divided by seven without using a calculator.

Answer 1

The angle
`(\pi)/(7)` is in Quadrant 1 and cos of an angle in quadrant 1 is always positive

Answer 2

The
`\cos (\pi)/(7)` has positive sign.

Explanation:

we need to determine the sign of
`\cos (\pi)/(7)` without using calculator

Cartesian system ( shown in figure -1)

The angle
`\cos (\pi)/(7)` lies in quadrant-1 , Where angles are zero (0) to
`(\pi)/(2)`

and in first quadrant all trigonometric ratios has positive sign

so,
`\cos (\pi)/(7)` has positive sign.