Half angle identities

vdub

Hi
Has anyone got any good links for resources and reading on said topic and their application?
Thanks in advance

Reply 1

OP

rbnphlp

here

In your failed attempt at humour or facetious juvenile 'wit' I can only laugh at how pathetic the attempt was.
I am fully aware I can google the same term you have...bravo..
That is not the question I asked is it?

Read the question again.... Good...I am looking for suggestions based on experience.
Its like asking a local where a GOOD place to eat is and them handing you the yellow pages....what use it that?

Anyway...bump this for anybody with (i) a helpful sides or (ii) someone with humour

vdub

...

If you pm me with your email address I will send you a Powerpoint on half tangent identities.

Reply 4

vdub

OP

Thanks very much
My faith has been restored in the board!
I have pm'd you

Reply 5

insparato

15

They're used in integrals of the form

\int \frac{1}{d + esinx + fcosx}

and

\int \frac{1}{a + btanx}

The usefulness comes from the fact that you can put cosx and sinx in terms of tan x/2 and so you make the substitution t = tan x/2, dt/dx = ..... and then from half angle manipulation you can put cosx and sinx in terms of t. Colloquially i think they're called T substitution formula.

I have to say I don't think I've ever had to use half angles formulas, except for integration.

Reply 6

rbnphlp

11

vdub

In your failed attempt at humour or facetious juvenile 'wit' I can only laugh at how pathetic the attempt was.
I am fully aware I can google the same term you have...bravo..
That is not the question I asked is it?

Read the question again.... Good...I am looking for suggestions based on experience.
Its like asking a local where a GOOD place to eat is and them handing you the yellow pages....what use it that?

Anyway...bump this for anybody with (i) a helpful sides or (ii) someone with humour