圖片參考:http://imgcld.yimg.com/8/n/HA00510450/o/20130921191432.jpg
2.Two electric motor pull a box with force F1= 3i +4j +5k and F2= 2i -3j -2k respectively. Determine the resultant force on the box.(麻煩中文解釋)
更新1:
我第1題都計到同你一樣,但ans:(−9i−3j+3k) /√45 咁可能係ans錯
更新2:
an angle with the positive x-axis (East) of -60 degrees 係5係姐係係象限IV?