Basic Trignometry: f(α).f(β) When α+β=5π/4

[suresh]

Homework Statement

Let f(θ)=cotθ/1+cotθ and α+β=5π/4
then the value of f(α).f(β) is:

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)

 

[NascentOxygen]

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

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: (((((((((()))))))))

 

[tms]

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

 

[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

 

[NascentOxygen]

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

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

 

[tms]

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

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.

 

[Ray Vickson]

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

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).

 

[adjacent]

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

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 #.

 

[micromass]

LaTeX guide: https://www.physicsforums.com/showpost.php?p=3977517&postcount=3