[shwan]

|AxB|=|A||B| sin t
|A.B|=|A||B|cos t
|AxB|=4
|A.B|=5
tan t= 4/5
t = arctan(4/5)


A=3i, B= -4j
AxB=-12k
A-B=3i+4j
A+2B=3i - 8j
A.B=0