Exceeding a means AD, and vertical BC means d.

Then AD=c×sin angle b=b×sin angle C.

sinb=sin(2c)=2sinc×cosc

C×2sinc×cosc=b×sin angle c

b=2c×cosc

Angle b=2 Angle C, Angle b+ Angle C.

So 0

1/2 & lt； cosc & lt 1

c & ltb & lt2c

2ac & lt2ab & lt4ac

The relationship between ac and 2ab 2ac