Will solving with a triangle using momentum instead of setting up as vector cross products work in every scenario?

9. A 1 kg mass that is moving east at 9 m/s collides with a 2 kg mass that is moving north at 6 MS. The two masses stick together. What is the speed of the resulting 3 kg mass just aer the collision? 7. om. magpie! :12. P: lg Th 6m/s ,3 2kg 9:11 \\5 @235: $ /\\ 9A )2/\\ V5 .: x : ,4 - Sift/s E; W *3 5\" Wig E.10m/s l? : mlN-Jf'chf