Question

How do you evaluate `cot 400`?

Answer 1

`cot400^o=1.1918`

Explanation:

Al trigonometric ratios are in a cycle of `2pi` radians or `360^o` i.e. their values repeat after `2pi` radians or `360^o`,

Hence, `cotx=cot(360^o+x)=cot(720^o+x)=cot(x-360^o)=cot(x-720^o)` etc.

Hence `cot400^o=cot(360^o+40^o)=cot40^o`

and from tables `cot40^o=1.1918`