E1xe1= | e1| x | e1| xcos0 =1e2xe2 is also e1xe2 = | e1| x | e2.

The final result is equal to -7/2.

The latter uses the formula cos@=(axb)/(|a|x|b|). . . . ( 1)

|a|= radical number [(2e 1+E2) 2] = radical number 7 |b|= radical number [(-3e 1+2e2) 2] = radical number 7 axb is a problem =-7/2.

Bring in (1) to get-1/2.

@= 120

After playing for a long time, you adopted it/(ㄒㄒ o)/~ ~