The first problem, according to the transformation relationship between the angle and the edge of the triangle, obtains the size of the angle B, and then solves it according to the problem. The second question is derived from the triangle area formula and the angle-edge relationship, and from the formula A+B >. When the root number is 2, ab finds the minimum value. This question examines the transformation between angle, edge and area through formulas. It's not difficult. I can work out the formula myself.