The limit problem is as follows:
.
Some thoughts I had about solving this were to express the inverse of tangent as a fraction of cosine divided by sine:
. By doing this I thought that I could then use the
theorem(?) to multiply the numerator by 21 yielding
which equals one. But I don't really know what to do with cosine and this is where I am stuck. The answer in the book is
. If someone could help point me in the right direction I would really appreciate it.
(P.S., sorry if this is in the wrong forum)