Recent content by terhje

lol. AB x AC = 0 implies that the vectors are parallel! my norwegian mathbook said nothing about it. Had to look in a calculus book i ordered from the states that i haven't had time to go through yet. fixed some typos.

That AB or AC or both are zero. Ill just show you what i got so far, which i think is the correct solution. Question: Check if the following points, A(-1,3,4), B(0,5,7), R(0,3,6) and S(1,5,9) are in the same plane. My solution: making vectors, AB, AC and AD AB= i+2j+3k AC=i+2k AD=2i+2j+5k...

I can check if AD is perpendicular to ABxAC, by checking if the dot product goes to zero. I was thinking it would leave room for D beeing in a parallel plane, but AD can't be in a parallell plane cause A already is in the ABC plane. Meaning AB and AD can't both go to zero if D was in a parallel...

Sorry, math is not my strong suit, but I am trying to learn. I saw them doing it here: https://www.math.washington.edu/~king/coursedir/m445w04/notes/vector/normals-planes.html#cross under: Normal Vectors and Cross Product Did i miss something?

Thanks for the help, Math_QED, I think I am at a solution. I found the equation of the ABC plane by taking the cross product of AB and AC vectors. Then taking the dot product of D and the plane equation. and checking if i get the same number as with the other points in the ABC plane.

Hello guys, How can i check if coordinantes A,B,C and D are in the same plane? 3D space(x,y,z) Can i take the cross product: AB x AC and check if its perpendicular to for example DC x DB. and then check if the crossproducts are parallell? but i guess this can give me two parallell vectors in...

lol, thanks for the help :D

Homework Statement Write this complex number in the form "a+bi" a) cos(-pi/3) + i*sin(-pi/3) b) 2√2(cos(-5pi/6)+i*sin(-5pi/6)) Homework Equations my only problem is that I am getting + instead of - on the cosinus side.(real number) The Attempt at a Solution a) pi/3 in the unit circle is 1/2...