Examination of knowledge points: 1. Trigonometric function relation 2. The relationship between roots and coefficients.

Give you an idea: I have long forgotten the specific coefficient relationship. It seems that the relationship between root and coefficient, x 1+x2=-6 x 1*x2=7 can solve the problem. I hope it helps you. tan(α+β)=(tanα+tanβ)/( 1-tanαtanβ)

According to these two formulas, the final result is tan (a+b) =-6/(1-7) =1. Since the range of a and b is (-π, π), we can get A+B=π/4 or 3π/4.

I look forward to helping you.

Work hard, son.

Analyze the problem slowly by yourself.

List all the relevant knowledge points and solve them step by step.