Thread: Help with Compound Angle Formulae

Hi guys! How do you solve this question?

1. Tan 75° (using the compound angle formulae)

8. a) Develop formulas for cot(α + β) and cot(α - β).
b) Find cot 75° + cot 15° without using tables.

10. a) Develop formulas for the following.
i) tan 2α
ii) cot 2α

Thank you!

Originally Posted by finalfantasy

Hi guys! How do you solve this question?

1. Tan 75° (using the compound angle formulae)

recall that

now, you can write as

now apply the formula


can you continue?

8. a) Develop formulas for cot(α + β) and cot(α - β).
b) Find cot 75° + cot 15° without using tables.

use the fact that

you know the addition formulas for sine and cosine right?

10. a) Develop formulas for the following.
i) tan 2α
ii) cot 2α

Thank you!

again, write as

and as

and apply the double angle formulas for sine and cosine

hmm ... I tried doing tan (45 + 30) and attempted to solve it, but i kept getting the wrong answer!