# Thread: Rate of change of trig function

1. ## Rate of change of trig function

Hi,

I hope someone can help. I'm suppose to state two intervals where the function y = 3cos(4x)-4 has an AROC that is zero. I'm wondering why my textbook only gave the solution of 0 < x < pi/2, and pi < x < 3pi/2 ? Wouldn't the two intervals 0 < x < pi/2, and pi/2 < x < pi be just as correct?

Sincerely,
Olivia

2. ## Re: Rate of change of trig function

actually, there are an infinite number of intervals ... wherever $f(b) - f(a) = 0$

the attached graph shows but a few intervals where the avg rate of change equals zero ...

3. ## Re: Rate of change of trig function

So are you saying that both the textbook's solution and mine are correct?

yes