# Absolute Extrema, Local Extrema

• Nov 23rd 2009, 02:48 AM
Johnny Walker Black
Absolute Extrema, Local Extrema
1)Find the absolute extrema of f(x) = sin x - cos x on the interval [ 0,∏ ].

Answer: abs. max at √2 or (sqrt.2) at 3∏/4.

2) State the intervals on which f(x)= cos x - sin x is increasing on the interval [-∏ , ∏], and name all the local extrema.

http://i754.photobucket.com/albums/x...Picture1-3.png

Could use some advice and help getting started thx.
• Nov 23rd 2009, 02:59 AM
HallsofIvy
I don't understand what you mean by "throwing trigonometric identities into the equation". What can you do on, say, f(x)= sin(x)- cos(x)? Have you found its derivative?
• Nov 23rd 2009, 03:08 AM
Johnny Walker Black
Quote:

Originally Posted by HallsofIvy
I don't understand what you mean by "throwing trigonometric identities into the equation". What can you do on, say, f(x)= sin(x)- cos(x)? Have you found its derivative?

dy/dx = cos(x)+sin(x)
cos(x)+sin(x)=0
here's where i'm stuck how should i go about solving for x?