# Homework Help: Basic trignometry

1. Jun 20, 2014

### suresh

1. The problem statement, all variables and given/known data
Let f(θ)=cotθ/1+cotθ and α+β=5π/4
then the value of f(α).f(β) is:

3. The attempt at a solution
f(α)f(β)=
(cotα/1+cotα)* (cotβ/1+cotβ)

= cotα.cotβ/((1+cotα)(1+cotβ))
=cotα.cotβ/(1+cotβ+cotα+cotα.cotβ)

Last edited: Jun 20, 2014
2. Jun 20, 2014

### Staff: Mentor

Hi suresh. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

Was there supposed to be an accompanying question?

When you have an answer, you could always check it by taking any value for α then using your calculator.....

Double-check by taking another value.

Also, your expressions above appear to be invalid, owing to a dearth of essential brackets. To help you fix this, please accept some spares I happen to have lying around: (((((((((()))))))))

Last edited by a moderator: May 6, 2017
3. Jun 20, 2014

### tms

You should be looking for relevant trigonometric identities, sum- of-angles identities, and the law of tangents.

4. Jun 20, 2014

### suresh

Thanks for all the help guys sorry for not writing clearly if only I knew how to put fractions
Also sorry for using some other symbol which I thought was pi and confusing all of you

5. Jun 20, 2014

### Staff: Mentor

You mean like this? Let f(θ)=cotθ/(1+cotθ)

Whatever the symbol was that you originally used, I read it as Pi.

6. Jun 20, 2014

### tms

You get
$$f(\theta) = \frac{\cot\theta}{1 + \cot\theta}$$
by typing "f(\theta) = \frac{\cot\theta}{1 + \cot\theta}" in TeX mode. You get TeX mode by either putting your equation inside double dollar signs or inside tex tags.

7. Jun 20, 2014

### Ray Vickson

Doing fractions is easy: if you have just $\frac{a}{b}$ it is sufficient to type a/b. If you have something like $\frac{a}{b+c}$ then you absolutely must use parentheses, but it is easy also: just type a/(b+c).

8. Jun 21, 2014

I recommend you to use latex all the time.

You only have to write \pi for $\pi$
And \frac{a}{b} for $\frac{a}{b}$

Use two # signs between the latex code to render it inline.
Use two \$ signs between the latex code to render it indented and on a separate line. This can be useful for writing large equations which are rendered stupidly using two #.

9. Jun 21, 2014