recall that

now, you can write as

now apply the formula

can you continue?

use the fact that

8. a) Develop formulas for cot(α+β) and cot(α - β).

b) Find cot 75° + cot 15° without using tables.

you know the addition formulas for sine and cosine right?

again, write as10. a) Develop formulas for the following.

i) tan 2α

ii) cot 2α

Thank you!

and as

and apply the double angle formulas for sine and cosine