Question

Need help with a vector question.

Which is a right angle triangle

ABC were A(3,1) B(-2,3) C(5,6)
STU were S(4,6) T(-3,7) U(-5,-4)

I can't graph it since I have to use vectors to solve it.

I tried it by finding the magnitude and using cosine law to try to find the angle, but it didn't work

Answer 1

The dot product of two vectors is 0 when they are orthogonal (meet at a right angle)

Answer 2

So try to take the dot product of all the sides in pairs

Answer 3

so I will turn each point into a vector, them multiply all the x together and y together then add the y and x to see if I get 0

Answer 4

Vector AB = <-5, 2> since to get a vector between two points you subtract the terminal coordinates from the initial coordinates

Answer 5

You don't turn the points into vectors, you get the vector between the points

Answer 6

sorry, I meant find the vector between the points

Answer 7

AC = <2, 5>

Answer 8

Its ok to make mistakes, you don't have to say sorry

Answer 9

AB dot AC = 0

Answer 10

The dot product is multiplying components and adding the results so we get -10 + 10 =0

Answer 11

That's enough right there, no need to keep checking other pairs

Answer 12

ok, and could you explain one question to me, because I don't understand why its not possible to do

Answer 13

ok go ahead

Answer 14

u=[3, -5] v=[-6,1] w=[4,7] why is u+v dot w not possible .

Answer 15

It depends on how you order it, (U + V) dot W is possible because U+V is a vector and W is a vector and you can dot the two vectors

But U + (V dot W) is not possible because V dot W is a number (not a vector and you can't take a vector like U and add a number to it.

Answer 16

my book says its not possible;e bc its sum is of a vector and scalar.

Answer 17

That is the second line of thought that I wrote. If you dot first V dot W is a scalar. You can't then turn around and add this scalar to the vector U

Answer 18

Is that understandable?

Answer 19

ok. So i'm using bedmass to solve it, thats why its doesn't work, bc I will be multiplying then adding

Answer 20

If bedmass = Please Excuse My Dear Aunt Sally, then yes you are multiplying before adding.

Answer 21

???

Answer 22

hey, could I ask you another question