Math Is Fun Forum

Dharshi

Member

Registered: 2006-10-31

Posts: 56

Anyone knows this??

Which of the following functions is non periodic ?
(a) f(x) = {x}, the fractional part of the number x
(b) f(x) = cot(x + 7)
(c) f(x) = 1 – sin^2x/(1 + cotx) – cos^2x/(1 + tanx)
(d) f(x) = x + sinx

Stanley_Marsh

Member

Registered: 2006-12-13

Posts: 345

Re: Anyone knows this??

Here a method , assume k are their period. Check out whether the equation F(x)=F(x+k) has a constant solution for k for any x.

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Numbers are the essence of the Universe

Stanley_Marsh

Member

Registered: 2006-12-13

Posts: 345

Re: Anyone knows this??

The first one, Let f(x)={x}={x+k} k must equally to any integers, the min period is 1
The second , let f(x)=cot(x+7)=cot(x+7+k) , since the period of cot is

then k=

Last edited by Stanley_Marsh (2007-03-13 20:08:25)

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Numbers are the essence of the Universe

Stanley_Marsh

Member

Registered: 2006-12-13

Posts: 345

Re: Anyone knows this??

The third one ,

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Numbers are the essence of the Universe

Stanley_Marsh

Member

Registered: 2006-12-13

Posts: 345

Re: Anyone knows this??

The fourth one ,

which is not below 0 , so the value of the function will always increase ,such function contains no period.

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Numbers are the essence of the Universe

Prakash Panneer

Member

Registered: 2006-06-01

Posts: 110

Re: Anyone knows this??

a) It is a fractional part. So, it is a periodic function.

b) Trigonometric function: It is also a periodic function.

c) Constant + or - Trig. function: Periodic function

d) Varibles +Trig : Non- periodic.

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Letter, number, arts and science
of living kinds, both are the eyes.

gig

Member

Registered: 2007-03-19

Posts: 3

Re: Anyone knows this??

a piece of timber is cut in two lenghts in the ratio of 7:2. if the original piece of timber was 828 cm long,how long is the larger piece of the cut lenghts.

Maelwys

Member

Registered: 2007-02-02

Posts: 161

Re: Anyone knows this??

a piece of timber is cut in two lenghts in the ratio of 7:2. if the original piece of timber was 828 cm long,how long is the larger piece of the cut lenghts.

To figure this out, you have to do a couple steps.
- First, since the ratio is 7:2, you add those together to determine how many total "units" the timber can be broken into.
- Then divide the length by the number of units, to find the length of each unit.
- Then, simply multiplying the length of each unit by the number of units length you want to calculate will tell you how long that piece is.

Stanley_Marsh

Member

Registered: 2006-12-13

Posts: 345

Re: Anyone knows this??

well , if a timber cut in 7:2 . you can think like this , 7 blocks of wood belong to A , 2 blocks of wood belong to B , then what is the total blocks of wood , the wood is cut in 7+2=9 blocks , then how long is each block , 828/9.   Then how long is 7 blocks together (larger) , (828/9)*7.

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Numbers are the essence of the Universe