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From: commengr on 20 Nov 2009 12:19
Hi,

Can some expert tell me the simplest method to find the max and min value
of a composite signal. For eg. if it is given as,

x(t) = sin(10*pi*t) + 2*cos(7*pi*t) + 3*sin(3*pi*t)

I can find the max and min values using Matlab, however, is there a method
to find it without using a software? Simply using a pen and paper?

Also, I don't want to have trial and error (Obviously).

Thanks.

Ps. Not a HW prob
From: Eric Jacobsen on 20 Nov 2009 12:24
On 11/20/2009 10:19 AM, commengr wrote:
> Hi,
>
> Can some expert tell me the simplest method to find the max and min value
> of a composite signal. For eg. if it is given as,
>
> x(t) = sin(10*pi*t) + 2*cos(7*pi*t) + 3*sin(3*pi*t)
>
> I can find the max and min values using Matlab, however, is there a method
> to find it without using a software? Simply using a pen and paper?
>
> Also, I don't want to have trial and error (Obviously).
>
> Thanks.
>
> Ps. Not a HW prob

Find the solutions for which the derivative is zero?

--
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com
From: commengr on 20 Nov 2009 12:33
>On 11/20/2009 10:19 AM, commengr wrote:
>> Hi,
>>
>> Can some expert tell me the simplest method to find the max and min
value
>> of a composite signal. For eg. if it is given as,
>>
>> x(t) = sin(10*pi*t) + 2*cos(7*pi*t) + 3*sin(3*pi*t)
>>
>> I can find the max and min values using Matlab, however, is there a
method
>> to find it without using a software? Simply using a pen and paper?
>>
>> Also, I don't want to have trial and error (Obviously).
>>
>> Thanks.
>>
>> Ps. Not a HW prob
>
>Find the solutions for which the derivative is zero?
>
>--
>Eric Jacobsen
>Minister of Algorithms
>Abineau Communications
>http://www.abineau.com
>

I had also thought of using that approach, however, I'm having
trigonometric functions. How is the derivative gonna be zero? Please
explain?
From: Rob Gaddi on 20 Nov 2009 12:37
On Fri, 20 Nov 2009 11:33:36 -0600
"commengr" <communications_engineer(a)yahoo.com> wrote:

> >On 11/20/2009 10:19 AM, commengr wrote:
> >> Hi,
> >>
> >> Can some expert tell me the simplest method to find the max and min
> value
> >> of a composite signal. For eg. if it is given as,
> >>
> >> x(t) = sin(10*pi*t) + 2*cos(7*pi*t) + 3*sin(3*pi*t)
> >>
> >> I can find the max and min values using Matlab, however, is there a
> method
> >> to find it without using a software? Simply using a pen and paper?
> >>
> >> Also, I don't want to have trial and error (Obviously).
> >>
> >> Thanks.
> >>
> >> Ps. Not a HW prob
> >
> >Find the solutions for which the derivative is zero?
> >
> >--
> >Eric Jacobsen
> >Minister of Algorithms
> >Abineau Communications
> >http://www.abineau.com
> >
>
> I had also thought of using that approach, however, I'm having
> trigonometric functions. How is the derivative gonna be zero? Please
> explain?

Well, d(sin x)/dx = cos x, d(cos x)/dx = -sin x, and for general
functions f(x) and g(x), d(f(x) + g(x))/dx = df(x)/dx + dg(x)/dx. The
rest is left as an example for the student.

See, and the teacher didn't think I was paying any attention in high
school calculus.

--
Rob Gaddi, Highland Technology
Email address is currently out of order
From: commengr on 20 Nov 2009 12:53
>On Fri, 20 Nov 2009 11:33:36 -0600
>"commengr" <communications_engineer(a)yahoo.com> wrote:
>
>> >On 11/20/2009 10:19 AM, commengr wrote:
>> >> Hi,
>> >>
>> >> Can some expert tell me the simplest method to find the max and min
>> value
>> >> of a composite signal. For eg. if it is given as,
>> >>
>> >> x(t) = sin(10*pi*t) + 2*cos(7*pi*t) + 3*sin(3*pi*t)
>> >>
>> >> I can find the max and min values using Matlab, however, is there a
>> method
>> >> to find it without using a software? Simply using a pen and paper?
>> >>
>> >> Also, I don't want to have trial and error (Obviously).
>> >>
>> >> Thanks.
>> >>
>> >> Ps. Not a HW prob
>> >
>> >Find the solutions for which the derivative is zero?
>> >
>> >--
>> >Eric Jacobsen
>> >Minister of Algorithms
>> >Abineau Communications
>> >http://www.abineau.com
>> >
>>
>> I had also thought of using that approach, however, I'm having
>> trigonometric functions. How is the derivative gonna be zero? Please
>> explain?
>
>Well, d(sin x)/dx = cos x, d(cos x)/dx = -sin x, and for general
>functions f(x) and g(x), d(f(x) + g(x))/dx = df(x)/dx + dg(x)/dx. The
>rest is left as an example for the student.
>
>See, and the teacher didn't think I was paying any attention in high
>school calculus.
>
>--
>Rob Gaddi, Highland Technology
>Email address is currently out of order
>

Your school calculus is real good. However, it does not help here.

I assume you are pointing that some terms might cancel... correct me if
I'm not following you... any way, since the trigonometric components have
different frequencies, they won't cancel each other out.

Let me elaborate, I want to *find* the max and min value of this composite
signal so that I can decide on the limits of the input voltage to a
quantizer. I don't want to 'put' external limits just yet.

Perhaps I need a reply from Robert B. J, Vlad etc

If anyone else can help, I'd welcome that too
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