Trig question

blacklionboy

Hi there,

This confused me in maths today.

if you have lets say: TanX/y

and then you change TanX to SinX/CosX

Do you get

a) SinX/yCos
or
b) SinX/CosX/y = ySinx/CosX

as well as saying what people get can people explain why

image attached to show question clearer

thanks

mathew

blacklionboy wrote: »

Hi there,

This confused me in maths today.

if you have lets say: TanX/y

and then you change TanX to SinX/CosX

Do you get

a) SinX/yCos
or
b) SinX/CosX/y = ySinx/CosX

as well as saying what people get can people explain why

thanks

ok.. do you mean tan(X/Y)

if you do, then using the formula you're talking about you get:
sin(X/Y)/cos(X/Y)

difficult to show here with just plain text.. ill try do something and put it as an image..

blacklionboy

Hi image now attached to original post to explain question better

mathew

right.. threw this together in word where I can write equations a bit better than on here.

The actual proof of the formula requires the unit circle as I mentioned which would take a while to draw and explain on my laptop with no proper mouse.

Also, I have no idea what perspective to explain it from (ie your level)

edit: no file, cause I realised i misinterpreted your question. Ill fix it and upload it again.

edit 2: Heres the new file!

Fringe

It's just simply
1/y . tan x
1/y . sinx/cosx
sinx/ycosx

TommyGunne

Sinx/Cosx/y != ySinx/Cosx.

That would be the mistake you are making. Not sure how to explain it well, but you have to remember where the important "/" is, because this makes a difference.

I've bolded the important "/" in equations below to highlight the difference.

1/2/3 = 1/6
1/2/3 = 3/2

I'm sure somebody has technical terms for what I've said here but I either never knew them, have forgotten them or there are none (or probably even better it was never reccommended to write fractions like that because it does cause confusion.) The logic is sound though.

So in your example, you have Tanx/y, so this is Sinx/Cosx/y, not Sinx/Cosx/y.

Hopefully this makes sense.

MathsManiac

TommyGunne wrote: »

Sinx/Cosx/y != ySinx/Cosx.

That would be the mistake you are making. Not sure how to explain it well, but you have to remember where the important "/" is, because this makes a difference.

I've bolded the important "/" in equations below to highlight the difference.

1/2/3 = 1/6
1/2/3 = 3/2

I'm sure somebody has technical terms for what I've said here but I either never knew them, have forgotten them or there are none (or probably even better it was never reccommended to write fractions like that because it does cause confusion.) The logic is sound though.

So in your example, you have Tanx/y, so this is Sinx/Cosx/y, not Sinx/Cosx/y.

Hopefully this makes sense.

Maybe veering off topic, but i think the term you were looking for is that division is not associative.