Ответ:

To find angle B, we can use the cosine rule:

cos(B) = (AB^2 + BC^2 - AC^2) / (2AB * BC)

Substituting the given values, we get:

cos(B) = (2^2 + 4^2 - (2sqrt(3))^2) / (2*2*4)

cos(B) = (4 + 16 - 12) / 16

cos(B) = 8/16

cos(B) = 1/2

Taking the inverse cosine of both sides, we get:

B = cos^-1(1/2)

B = 60 degrees

Therefore, angle B is 60 degrees.