So our idea is: vector A times vector B, divided by the modulus of vector A times the modulus of vector B.
First, multiply the two vectors of ab, that is, (2e 1+e2) times (3e 1+2e2).
It should be noted that when e 1 is multiplied by e2, the remaining chord values are cos60= 1/2.
Then find the value of a, that is, use 2e 1+e2 square, that is, the modulus of a is equal, that is, multiply two A's. Gets the value of
Similarly, the value of b is obtained.
Finally, the included angle of ab is obtained.
You have to work out the answer yourself! ! !