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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: Tea.bag on November 06, 2008, 09:06:37 pm

Title: help
Post by: Tea.bag on November 06, 2008, 09:06:37 pm: whats the period of |3cos(2x)|?
Title: Re: help
Post by: cinnamonbun on November 06, 2008, 09:07:12 pm: pi/2 i think
Title: Re: help
Post by: danieltennis on November 06, 2008, 09:11:15 pm: Quote from: Tea.bag on November 06, 2008, 09:06:37 pm
whats the period of |3cos(2x)|?

Its just pi/2.
Edit:(opps)
Title: Re: help
Post by: trinon on November 06, 2008, 09:12:54 pm: Quote from: danieltennis on November 06, 2008, 09:11:15 pm
Quote from: Tea.bag on November 06, 2008, 09:06:37 pm
whats the period of |3cos(2x)|?

Its just pi.

No, its $\frac{\pi}{2}$
Title: Re: help
Post by: cinnamonbun on November 06, 2008, 09:15:22 pm: Quote from: danieltennis on November 06, 2008, 09:11:15 pm
Quote from: Tea.bag on November 06, 2008, 09:06:37 pm
whats the period of |3cos(2x)|?

Its just pi.

its pi on 2 cos wen u hav absolute function it reflects in the x axis right? so the period becomes half as the cycle is like halved.. try draw it xP
Title: Re: help
Post by: spudman on November 06, 2008, 09:19:27 pm: the what occurs when u get |3cos2x + 1|?
Title: Re: help
Post by: cinnamonbun on November 06, 2008, 09:20:32 pm: the period shood still be the same
edit: oh wait
no its not
i have no idea wut the period wood be

edit: i think the period wood be pi XD
Title: Re: help
Post by: Quickclaw on November 06, 2008, 09:40:01 pm: wouldn't it stay the same because the only thing you are changing is reflecting the negative part of the graph, so it would be $\pi$ ?
But on the other hand, the graph is repeating each $\pi/2$ interval which would define a period, so I actually go with $\pi/2$ lol
Title: Re: help
Post by: AppleXY on November 06, 2008, 09:45:41 pm: Sorry,

Is it |3cos(2x) + 1| or |3cos(2x+1)|

it makes a big difference. :)
Title: Re: help
Post by: Collin Li on November 06, 2008, 10:53:51 pm: Quote from: AppleXY on November 06, 2008, 09:45:41 pm
Sorry,

Is it |3cos(2x) + 1| or |3cos(2x+1)|

it makes a big difference. :)

[Incorrect information]
Title: Re: help
Post by: vce08 on November 06, 2008, 10:58:47 pm: Are you sure coblin?
Say the graph |3cos(2x) + 4|
That would have a period of pi,
Whilst the graph of |3cos(2x)| + 4 would have a graph of pi/2 right?
Title: Re: help
Post by: onlyfknhuman on November 06, 2008, 11:03:05 pm: edit: im wrong i follow collin :D
Title: Re: help
Post by: Collin Li on November 06, 2008, 11:08:12 pm: Quote from: vce08 on November 06, 2008, 10:58:47 pm
Are you sure coblin?
Say the graph |3cos(2x) + 4|
That would have a period of pi,
Whilst the graph of |3cos(2x)| + 4 would have a graph of pi/2 right?
Quote from: onlyfknhuman on November 06, 2008, 11:03:05 pm
no both have a period of pi/2

translations do not affect period.

Actually, yeah I agree with vce08. The translation matters because the modulus has a special effect on the period in this case. It depends on the inside function being centered at zero.
Title: Re: help
Post by: vce01 on November 06, 2008, 11:11:18 pm: shit, what effect does the absolute function have on the period? for sin/cos and tan? do you just find the normal period and times it by 1/2?
Title: Re: help
Post by: Collin Li on November 06, 2008, 11:14:02 pm: Imagine $|\sin x|$ . That has a period of $\pi$ instead of $2\pi$ because all of a sudden all the negative parts are reflected to become exactly the same as the positive parts.

However, $\left|\sin x + \frac{1}{2}\right|$ doesn't have that same effect. It will still have some reflection, but it will not halve the period.