Recent content by Hacca

An absolute value property is $$\lvert a \rvert \geq b \iff a\leq-b \quad \text{ or } \quad a\geq b,$$ for ##b>0##. Is this true for the case ##a=0##? I mean if ##a=0, \lvert a \rvert =0## so ##0 \geq b##. But ##b## is supposed to be ##b>0##, so we have a contradiction. How can this property...

Vector fields confuses me. What are the differences between (##t## could be any variable, not just time): 1. If the position vector don't have an argument, ##\mathbf{r}=x\mathbf{\hat e}_x+y\mathbf{\hat e}_y+z\mathbf{\hat e}_z=(x,y,z)## so ##\mathbf{E}(\mathbf{r},t)=E_x(\mathbf{r},t)\mathbf{\hat...

Thanks, I have never seen this methods. The textbook & teacher only use pi(f(x))² and Washer method. Should it not be possiable with disc/washer? With [0,1] I got: Vy = 4\pi ((1-\frac{1}{4*1}-ln1) - (\frac{0}{0}-\frac{1}{4*0}-ln\frac{0}{0})) = 4\pi (1-\frac{1}{4}) = 4\pi (3/4) Isn't the...

Homework Statement Hello! English is not my native language so I hope the terminology is right. Q: Find the volume generated by the curve y=1/x+2, positive x- and y-axis and the line x=1. Calculate the volume obtained by rotation around the: a) x-axis b) y-axis Homework...