Post by: Piney.z on May 29, 2008, 06:12:28 pm
a) find the gradient function,
and soo i got
and then draw the graph of dy/dx.
but thenn laterr it ask to
c) sstate the coordinates of the point on the track for which the magnitude of the gradient is maximum.
and thus.. now i'm stuck ??? i dont really get the minimum and maximum thing......
help? :)
Post by: excal on May 29, 2008, 06:17:04 pm
(In other words, the rate of change of your gradient function).
Consider your circular functions sin/cos. When you have the maximum or minimum, the gradient will be zero. Thus, when you have your derivative of the gradient function (or double derivative of the original function), you just need to find the solutions to it.
Of course, you'll need to work out which ones are the maximums and minimums, but you should be able to do that when you graph all three ... :)
Post by: cara.mel on May 29, 2008, 06:25:46 pm
However, his "Consider your circular functions sin/cos" without continuing on the proper way of thinking reminded me on something.
On a normal sine/cosine curve, the gradient is the maximum when it crosses the x axis. So they will be in those spots.
(you can confirm this by taking the derivative and solving for 0, which is solving cos pi x/80=0. You just don't actually need to calculate anything new :))
Post by: excal on May 29, 2008, 06:32:38 pm
Post by: Piney.z on May 29, 2008, 06:37:24 pm
i think i'm following with what you're saying.
one question though,
if we're doing both methods and specialist..
can we use the knowledge of spesh to apply it in methods exams?
such as the second derivative which isn't learn in methods?
Quote
I'm getting there!Lol! okok :P
Post by: cara.mel on May 29, 2008, 06:42:14 pm
one question though,
if we're doing both methods and specialist..
can we use the knowledge of spesh to apply it in methods exams?
such as the second derivative which isn't learn in methods?
You should generally try to avoid it. Eg on the topic of this, if in methods you have to show something is a min/max, don't find 2nd derivative, do one of them sign diagram things.
And joe, don't be like everyone else and post
-question line here-
*working*
then edit 50 times, so you get glory of first post. xD
Post by: excal on May 29, 2008, 06:42:40 pm
given we know that
Now our horizontal dilation factor is
Post by: excal on May 29, 2008, 06:42:59 pm
Post by: cara.mel on May 29, 2008, 06:44:15 pm
So you don't complain about first posting.
Thanks. I love you :smitten:
Post by: ed_saifa on May 29, 2008, 06:45:46 pm
mmm. okay.It is ok to use specialist techniques in methods providing the question doesn't specifically ask for a particular method to be used. For example, using the second derivative in place of a sign diagram.
i think i'm following with what you're saying.
one question though,
if we're doing both methods and specialist..
can we use the knowledge of spesh to apply it in methods exams?
such as the second derivative which isn't learn in methods?QuoteI'm getting there!Lol! okok :P
Post by: excal on May 29, 2008, 06:46:47 pm
Post by: Piney.z on May 29, 2008, 06:53:12 pm
is there anywhere which was said by VCAA that we're allowed/ not allowed?
since there's 2 answers.... :-\
#######################
ohh. i forgot to mention that
does that make a difference?
because the answer is (40,12)
...
Post by: cara.mel on May 29, 2008, 07:00:14 pm
Excalibur == anhero (I'm learning!)
He did 160/4 = 45, and then used wrong equation somehow :P
Simply:
Find that period = 160
Remeber that cos(x) = 0 at 1/4 and 3/4 of period (40, 120, 200 etc)
Sub in 40 into equation and get y=12
Post by: excal on May 29, 2008, 07:00:25 pm
You plug the
So,
therefore, (40,12).
I'm not thinking straight.
Post by: Piney.z on May 29, 2008, 07:33:43 pm
gotcha now. =]
tyty
cool beans xD
Post by: Mao on May 30, 2008, 05:34:02 pm
I have heard from teachers that spec and methods get treated very differently in terms of "exotic" methodsmmm. okay.It is ok to use specialist techniques in methods providing the question doesn't specifically ask for a particular method to be used. For example, using the second derivative in place of a sign diagram.
i think i'm following with what you're saying.
one question though,
if we're doing both methods and specialist..
can we use the knowledge of spesh to apply it in methods exams?
such as the second derivative which isn't learn in methods?QuoteI'm getting there!Lol! okok :P
in MM, I dont think you are allowed to use non-methods knowledge to answer questions [i.e. if you need to prove the nature of turning points, you are not allowed to use second derivatives]
in SM, however, so long as the question does not specifically ask for it, you are not bound so long as you get the answer [within reason, that is, doing a proof using imaginary numbers for sin(80)=cos(10) is really unecessary :P]
however, dont take this as absolute, i can be wrong
Post by: /0 on May 30, 2008, 08:47:50 pm