RE: max/min of trig

[Martoman]

This is annoying me. Trying to help a friend out but can't see what's wrong with this line of reasoning.

Find the max/min of

1) Isolate the terms

2) Consider max and min points. They are 1,2,6 for max, similarly 0, -2 and 6 for min.

3) Sum of max values give max, similarly with min.

Hence Max = 9, Min = 4

But its obviously the min = 5. Whats wrong?

[brightsky]

Err...remember that the in is equal to the in . The that would yield the lowest value for is obviously . So substituting in, we get the values 1 - 2 + 6 = 5.

[Martoman]

oh ok. I just diffed and went from there. Of course, it flew over her head.

[kyzoo]

Mmm you can do this without differentiation.

First complete the square











Thus the maximum is 9, and the minimum is 4

[brightsky]

cannot equal to .

. For , which is impossible.


Reconsider last step.

, not 4.

[Martoman]

Kyzoo is correct brightsky, he is just mortal and made the mistake that 0+5 = 4. We do that as mathematicians. I have made it a habit of mine to call 2-1 = 21. It happens.

[brightsky]

Kyzoo is correct brightsky, he is just mortal and made the mistake that 0+5 = 4. We do that as mathematicians. I have made it a habit of mine to call 2-1 = 21. It happens.

lululz, sorry, I didn't mean for any offence.

[Martoman]

haha its all good.