Given that a + B + C = 0, the absolute value of a = 3, the absolute value of B = 5, and the absolute value of C = 7, find the cosine value of the cosine of the cosine angle between the vector 2A + 3b and the vector 3a-b

Given that a + B + C = 0, the absolute value of a = 3, the absolute value of B = 5, and the absolute value of C = 7, find the cosine value of the cosine of the cosine angle between the vector 2A + 3b and the vector 3a-b

In fact, from the equation, we can get that ABC is the three sides of the triangle. You can customize the coordinates of the two vertices of the triangle, calculate the coordinates of the third vertex according to the two sides of the three sides, and then all the three vectors of ABC come out. Sorry, I can only tell you the method, because I can't get a good point, with a root sign, and the answer is not normal

If the absolute value of vector a is 0, what's wrong with vector a = 0?
"If the absolute value of vector a is 0, then vector a = 0"

Vectors are not numbers
Vector a [not] 0
0 is [only] [length]
Vector 0 is [length 0, direction]