Question

Cot (15 degrees)

Find the two common angles that differ by 15 degrees. Rewrite this problem as the cotangent of a difference of those two angles.

Answer 1

We have to write 15 degree as the difference of two angles.

And

`15 = 45-30, 15=60-45`

Now we have to use the formula of cotangent of a difference of those two angles.

And the formula is

`cot( \alpha - \beta) = ( cot \alpha cot \beta +1)/( cot \beta -cot \alpha )`

THerefore,
`image`

And that's the required expressions .