Find the resultant moment and direction angles

Get the book here: amzn.to/2py6FIn
If F1 = 100 N, F2 = 120 N, and F3 = 80 N,
determine the magnitude and coordinate direction angles
of the resultant couple moment.
Determine the required magnitude of F1, F2,
and F3 so that the resultant couple moment is
(Mc)R = [50i - 45j - 20k] N # m.

[@romannikolin6522]

You're amazing, thank you for the effort you put in these videos.

[@Aurora-pp3cs]

WOOWWWWWWW you made this problem soo simple. I was looking for the solution on other websites where they solved it in a way that is very hard to understand. Then I luckily bumped into your video. I really appreciate it

[@sakariaahmad416]

ThAnks a lot

[@jackpeplinski9678]

If you are doing moment about a specified axis, as you do for M4, wouldn't you need to use the triple scalar product and multiply that by the unit vector?

[@bhumipatel5634]

Why are we finding the unit vector for calculating M4 and not also for M1,2 & 3?​

[@kyledeva]

In the Uab isn't the answer supposed to be 0.0707i and -0.0707j?

[@stuartaft]

I'm pretty sure vector AB should have a z-component of -0.1m k, since the height goes from 0.3m to 0.2m.

[@JonathanMartinez-ge4rg]

in chegg for m1 they had i istead of j vector