# One more area of region bounded by curves question...

• Feb 19th 2009, 07:26 PM
fattydq
One more area of region bounded by curves question...
I think I'm getting a good handle on these problems as I do more of them, but this one (I've attached a picture) is tough because it involves trig functions. The intersection points for x are -pi/39 0 and pi/39 so I thought I'd use the integral from -pi/39 to positive pi/39. After integrating and getting -1/13ln(cos(x))-(-2/13)cos(13x) and I keep getting 0. Obviously this isn't right. Where am I going wrong?
• Feb 19th 2009, 07:33 PM
skeeter
Quote:

Originally Posted by fattydq
I think I'm getting a good handle on these problems as I do more of them, but this one (I've attached a picture) is tough because it involves trig functions. The intersection points for x are -pi/39 0 and pi/39 so I thought I'd use the integral from -pi/39 to positive pi/39. After integrating and getting -1/13ln(cos(x))-(-2/13)cos(13x) and I keep getting 0. Obviously this isn't right. Where am I going wrong?

$\int_{-\frac{\pi}{39}}^0 \tan(13x) - 2\sin(13x) \, dx + \int_0^{\frac{\pi}{39}} 2\sin(13x) - \tan(13x) \, dx$
• Feb 19th 2009, 08:22 PM
fattydq
Ok...but why?
• Feb 20th 2009, 05:46 AM
skeeter
Quote:

Originally Posted by fattydq
Ok...but why?

look at the graph and see why.