已知向量a的绝对值=6,向量b的绝对值=4,a与b的夹角为π/6,求

1. a•b = |a| |b| cos(π/6) = 6 * 4 * √3/2 = 12√3 2. |a|^2 = 36 3. |a+b|^2 = (a+b)•(a+b) = |a|^2 + 2 a•b + |b|^2 = 36 + 2*12√3 +16 = 52 + 24√3 |a+b| = √( 52 + 24√3 )