some quick maths help

[Lemon[H]ead]

k, i have to solve the equation Sin2x-Cosx=0
I tried using the addition formula to get

Sin(x+x)-Cosx=0
SinxCosx+SinxCosx-Cosx=0
2SinxCosx-Cosx=0

but i can't get any further (i couldnt see what to substitute in). Can anyone help me, please.

Thanks

[Cruez]

Sorry, I failed at Greek symbology........at least thats what it looks like...

Really, I have no clue how to figure that out..

[caddmannq]

Hint: sine over cosine = tangent

[HomeYield]

Try:
http://www.sosmath.com/trig/Trig5/trig5/trig5.html

Maybe this'll help if you don't have the identities written down somewhere for you. Its been too long since I've done trig that I don't even remember what to solve for. Post the answer when you get it. I'd be interested in knowing what it is.

[Lemon[H]ead]

thanks

edit: I have no clue as to how this is done. None whatsoever. There are no values given (oh it has to be solved between 0 <= X <= 180)

edit2: and i know the answer is X=30, because i know that Sin60=��3/2 and Cos30=��3/2 (one minus the other=0). But i don't know how to get there through subsituting formulas in, etc.

[willy_ph]

That stuff brings back bad memories of Algebra/Geometry class from last year.

Ack! *runs away cowering*

[puk]

Sin2x-Cosx=0 a)
-------------------------
Sin2x=2SinxCosx b)

So a) is 2SinxCosx-Cosx=0 divide by Cosx

2SinxCosx/Cosx-Cosx/Cosx =0 ==> 2Sinx-1=0 ==> Sinx=1/2 ==> x=30



Puk

[Lemon[H]ead]

thanks m8!

i would never have thought to divide through by cosx in a million years. you just eased a big weight off my back (i have buttloads of formal assessments tommorrow and getting this question allowed me to get through the maths homework i'm doin)

[puk]

U'r Welcome

Puk

[caddmannq]

i would never have thought to divide through by cosx in a million years.

After I gave you the hint????

Sine over cosine = tangent?????

Didnt you know that "over" means "divide by"????

divide by the cosine!!!!

Aaaaauuuuuggggghhh