----(adsbygoogle = window.adsbygoogle || []).push({});

First question:

----

This first question is kind of weird. I'm not even sure where to go with it. If anyone has a hint, that would be awesome.

From [itex] \vec A \times \vec B = -\vec B \times \vec A [/itex] deduce [itex] \vec A \times \vec A = 0 [/itex]

Can it be as simple as:

let [tex] \vec B = \vec A_0 | \vec A_0 = \vec A [/tex]

thus: [tex] \vec A \times \vec A_0 = -\vec A_0 \times \vec A = 0 [/tex]

----

Second question:

----

Find the minimum and maximum speed if [itex] x=t+\cos t [/itex], [itex]y=t-\sin t [/itex].

Please allow me to take advantage of the inner space operator for sake of ease while writing the vectors :)

Thus:

[tex] \vec x = <t+\cos t,t-\sin t> [/tex]

[tex] \vec v = <1-\sin t, 1-cos t> [/tex]

So speed is computed as: [itex] |\vec v| [/itex]. Therefore the largest speed values that can occur are when: [itex] \vec v = <1,2> or <2,1> [/itex] and the lowest speed values that can occur are when [itex] \vec v = <1,0> or <0,1> [/itex].

Is this reasoning even correct with this problem?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Two Questions - calculus

**Physics Forums | Science Articles, Homework Help, Discussion**