matrix+ vector...

noob1988

怎样determine 3point are collinear?

數學神童

anyone can teach me further math?

antimatter

@1988: 不明白……
@數學神童: 你是神童咧，哪里还有人敢教你……

noob1988

@1988: 不明白……
@數學神童: 你是神童咧，哪里还有人敢教你……
antimatter 发表于 15-1-2010 12:16 AM

    four point p(2,3,1) q(4,2,2) r(8,0,4) and s(3,6,1)
determine whether the points p,q,r are collinear

题目是这样的...



还有一个

determine whether the following two lines are perpendicular

x=2+3t    y=4-t    z=1-2t
x=1+t     y=-3+2t    z=5t


u=<2,4,1>+t<3,-1,-1>
v=<1,-3,0>+t<1,2,5>

perpendicular是不是拿v.u=0?
我应该拿前面的还是那*t的？

antimatter

if (q-p)=c(r-p) ==> p,q,r are collinear, c can be any real scalar.

*t 的。

noob1988

if (q-p)=c(r-p) ==> p,q,r are collinear, c can be any real scalar.

*t 的。
antimatter 发表于 15-1-2010 09:04 AM

    谢了...


再来...
find the volume of the parallelepiped determined by the vectors a=(6,3,-1),b=(0,1,2)and c(4,-2,5)


found the solution...lol

帮我看看对不....
V=|a.(bxc)|
b x c=
|i    j     k|
|0   1    2|=9i+8j-4k
|4   -2   5|

a.(bxc)=54i+24j+4k

V=(54^2+24^2+4^2)^1/2
V= 59.23 units^3?

antimatter

V=|a.(bxc)|

这个应该对，剩下的没看。

noob1988

find the determinant of matrix 4*4
eg

|2 4 0  1|
|0 0 7  0|
|-1 1 2 3|
|2 3 -1 0|

can i use 2(det matrix3x3)-4(det matrix3x3)+0-1(det matrix3x3)？

antimatter

I tot the general method to find deteminant should be able to be found in textbook or notes? Think so.. i not quite sure..

noob1988

I tot the general method to find deteminant should be able to be found in textbook or notes? Think s ...
antimatter 发表于 16-1-2010 03:10 PM

    tis solution i saw in web...and my friends answer...
but note nvr c tis solution...
so i ask lo