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Column vectors 2015-02-21
From jill:
A has co- ordinates (7,-1) and B has co-ordinates (3,5).write these as column vectors
Answered by Penny Nom.
A column and a sloped ceiling 2011-06-10
From Tom:
Hi! I am a woodworker who needs some help finding a formula. I have to make a cylinder shape column that butts up against a sloped ceiling using bending plywood. I need to figure out how to cut the shape on this flat piece of material. The diameter of the column is 54.375". The tallest point is 9 13/16" and the shortest point is 4 7/16". Any help would be greatly appreciated.
Answered by Harley Weston.
The column space of a matrix 2009-02-12
From John:
Question from John, a student:


1 1 0 0
1 1 0 0
0 0 1 0
0 0 1 1


1 5 6
1 5 6
0 7 2
0 0 9

Is the space spanned by the columns of A the same as the space spanned by the columns of B?
Answered by Harley Weston.

Two-column proof for a circle geometry problem 2007-08-24
From Kendra:
i have to prove that tangents to a circle at the endpoints of a diatmeter are parallel by stating whats given, whats to prove and a plane, then write a two column proof i dont understand this
Answered by Stephen La Rocque.
Prove that a rhombus' diagonals are perpendicular 2005-10-02
From Tania:
How do you prove that a rhombus' diagonals are perpendicular using the 2 column proof method?
Answered by Walter Whiteley.
Two matrix problems 2005-03-30
From Sue:
Question 1
Suppose all matrices in the equation below are square and invertible. Solve for x .

BA-1XB-1 + 2BA + In = 0 (the symbol "0" here denotes the matrix of all 0's in it)

Also, A-1 or B-1 is indicating inverse and "In" = for example, A-1 times A
I hope you understand the above. I have to show all the steps.

Question 2
Suppose we consider the set of all 2x2 matrices along with the operations of matrix addition and multiplication. Do they form a field? Why or why not?
I think the answer is no because under multiplication it is not commutative and not all square matrices are invertible. I not positive so I'd like some help.

Answered by Penny Nom.
A matrix construction problem 2005-03-14
From Marcelo:
I want to know if is it possible to solve this problem:
I have an empty NxM matrix and I know totals (sum) by rows and totals by column.
Is there any algorithm to fill the matrix so that the summary of columns and rows gives the original values I have?

Answered by Harley Weston.



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