Posted by **miley** on Tuesday, March 30, 2010 at 9:40pm.

an electric current I , in amps is given by:

I= cos(wt) + sqrt of 3 sin(wt)

where w is positive constant. what are the max and minimum values of I?

*please be specific

- math/calculus -
**Reiny**, Tuesday, March 30, 2010 at 9:56pm
dI/dt = -wsin wt + w√3cos wt

= 0 for max min

wsin wt = w√3cos wt

sin wt/cos wt = w√3/w = √3

tan wt = pi/3 or 4pi/3

if wt = pi/3

I = cos pi/3 + √3sin pi/3 = .5 + 1.5 = 2

if wt = 4pi/3

I = cos 4pi/3 + √3sin 4pi/3 = -.5 -1.5 = -2

- math/calculus -
**miley**, Tuesday, March 30, 2010 at 10:02pm
so it could be pi/3 or 4pi/3

which means both are correct?

should i put both answers or one answer on my final paper?

- math/calculus -
**Reiny**, Tuesday, March 30, 2010 at 10:33pm
The pi/3 yields the maximum, notice I = +2

and the 4pi/3 yields the minimum

The actual question was, "what are the max and min values of I"

max of I is 2

min of I is -2

the pi/3 and 4pi/3 **produce** those max and mins, they themselves are not the max and mins.

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