Trig analysis question help.

[ausyid]

Something irrelevant is modelled by the formula:     y=2 sin⁡〖(3t- π/4)〗

   a) The maximum value of y is 10. State the minimum value
   b) Show that y attains a minimum value when t=7π/12.

I have done (b) and I get the answer -2. However I cannot see how this fits with (a)

Help me please. I am sure I am doing something fundamentally wrong.

Thanks.

(This is my first time asking a maths question. I tried to copy the equation from Word but it hasn't worked properly. Sorry)

[Collin Li]

The maximum value of cannot possibly be 10 if .

[ausyid]

That's what it says.

I couldn't understand it either.

I thought it might have something to do with expanding the brackets.

[Collin Li]

There is something fundamentally wrong with the question (most likely the equation) that is being displayed on the forum. It's not your mathematics.

only resides in the range . It doesn't matter what values you throw in there, can be anything (as far as Methods is concerned). will result in a maximum at 2, and a minimum at -2.

[doboman]

range---> [-2,2]

[ausyid]

It's a very simple question and both of you have got the same answer as me. So why is the question saying differently!?!?

[Collin Li]

Unless this is a SAC, don't bother with it. The question is incorrectly written (or has been incorrectly copied to the forums).

[ausyid]

It has been correctly copied.

I keep checking just to make sure.

This isn't a SAC, but it is part of a worksheet that will be marked and I want to do well

[Collin Li]

Oh well. Just ignore the statement about the maximum (which really has no bearing on your answers), and just go ahead.

The answer to part (a) is -2, and simply show that solving for yields as a solution.

I'd advise you to ask your teacher about it though, if it's gonna be marked.

[ausyid]

Apparently the problem with this question is that the formula is missing a +8 on the end (ie a translation 8 up)

Now if someone could just explain to me why I got -2 to be the minimum when it should surely be 6, then that would be great

[Collin Li]

Well, if you're working with , you won't get -2 any more. You'll get 6.

[ausyid]

Of course.

Thank you.