Variant: Angle A=30 degrees is changed to angle B=60 degrees, a=2, Equation 3, and B=6, and the triangle is solved.

Solution: Because A

So angle a is an acute angle.

According to sine theorem a/sinA=b/sinB

De: sinA=asinB/b

= (No.23) Sine 60 degrees /6

=[(2 root number 3)x (root number 3)/2]/6

= 1/2

So A=30 degrees, and angle C= 180 degrees -60 degrees -30 degrees =90 degrees.

So triangle ABC is a right triangle,

So c 2 = a 2+b 2.

=(2 formula 3) 2+6 2

=48

The root number 3 of C=4.