Recent content by jonnejon

So, y = A cos(3x) + B sin(3x) y' = -3A sin(3x) + 3B sin(3x) y = -A = 3 => A = -3 y'= -3B = 3 => B = -1 So the solution is: y= 3cos(3x) - sin(3x)??

Yes! I got it. Thanks Mark and Chewy. Yeah, I forgot to set my calculator back to radians, thanks for the help guys.

Oh yeah, did the algebra wrong... So, sinx/cosx = 1 = tanx x=45? so I should input the answer as: y = 5 e^(-45) sin(45)?

Homework Statement y'' + 9y = 0 where y(pi/3) = y'(pi/3) = 3Homework Equations r^2 + 9 = 0 r^2 = -9 r = 3i The Attempt at a Solution y = c1 e^x cos (3x) + c2 e^x sin(3x) y' = c1 e^x cos (3x) - 3c1 e^x sin (3x) + c2 e^x sin(3x) + 3c2 e^x cos(3x) y = -c1 e^(pi/3) = 3 => c1 = -3e^(-pi/3) y' =...

So, 0 = sin(x)/cos(x) = tan(x)? so tan (0)=0 so the max value of y is 0?

Yeah, I found out that you set the derivative to zero but as I said before I am terrible at trigonmetry. So: y'=5e^-x (cos(x)- sin(x)) 0=5e^-x (cos(x)- sin(x)) 5e^-x cos(x) = 5e^-x sin(x) cos(x) = sin(x) Whats next?

I am sorry, but I really don't know. I have been looking for awhile and I can't seem to find it. Did I do the differential equation correct though?

I really don't know, my professor moves way to fast and doesn't give enough examples. I also completely forgot about that. If you show me how to do it instead of giving hints, I am sure I will learn it better that way. I would really appreciate that. Thanks.

Yeah, I missed that but doesn't change my answer much. r = -1 +/- i I solved it: y = c1 e^-x cos(x) + c2 e^-x sin(x) y' = -c1 e^-x cos(x) - c1 e^-x sin(x) -c2 e^-x sin(x) + c2 e^-x cos(x) y = c1 = 0 y' = -c1 + c2 = 5 => c2 = 5 y = 5 e^-x sin(x) But I still can't find the max value of y...

Homework Statement Let y be the solution of the initial value problem: y'' + 2y' + 2y = 0 , y(0) = 0 , y'(0) = 5 The maximum value of y over 0 less than or equal to x less than infinity is ??. The Attempt at a Solution r = -2 +/- i I solved it: y = c1 e^-2x cos(x) + c2 e^-2x sin(x) y' =...

Homework Statement Find the magnitude of the torque about P if a 68 lb force is applied as shown. Give your answer correct to the nearest integer. Homework Equations t=r X FThe Attempt at a Solution t = (4)(68)(sin30) = 136

Anyone?

I can't seem to get this right, am I doing something wrong? Please help, its getting frustrating.

I did convert it into Pa 1 atm = 1.013e5 F = (1.013e5 Pa)(.08 m)^2(pi)= 2037 N, I submitted this but it says incorrect.

Homework Statement A cylinder with a 16-cm-diameter piston contains gas at a pressure of 3.0 atm. A.How much force does the gas exert on the piston? B.How much force does the environment exert on the piston? C.The gas expands at constant pressure and pushes the piston out 10 cm. How...