







Column vectors 
20150221 

jill pose la question : A has co ordinates (7,1) and B has coordinates (3,5).write these as column vectors Penny Nom lui répond. 





A column and a sloped ceiling 
20110610 

Tom pose la question : 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. Harley Weston lui répond. 





The column space of a matrix 
20090212 

John pose la question : Question from John, a student:
A=
1 1 0 0
1 1 0 0
0 0 1 0
0 0 1 1
B=
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? Harley Weston lui répond. 





Twocolumn proof for a circle geometry problem 
20070824 

Kendra pose la question : 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 Stephen La Rocque lui répond. 





Prove that a rhombus' diagonals are perpendicular 
20051002 

Tania pose la question : How do you prove that a rhombus' diagonals are perpendicular using the 2 column proof method? Walter Whiteley lui répond. 





Two matrix problems 
20050330 

Sue pose la question : Question 1
Suppose all matrices in the equation below are square and invertible. Solve for x .
BA1XB1 + 2BA + In = 0 (the symbol "0" here denotes the matrix of all 0's in it)
Also, A1 or B1 is indicating inverse and "In" = for example, A1 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. Penny Nom lui répond. 





A matrix construction problem 
20050314 

Marcelo pose la question : 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? Harley Weston lui répond. 

