∫ AC vertical BC

∴ Angle a+ Angle B = 90-( 1)

Vertical air conditioning

∴ angle a+ angle ade = 90.

* CD AB of ice

∴ angle ADE+ angle1= 90

∴ angle 1 = angle a

Angle 1 = angle 2

∴ Angle 2+ Angle B = 90 (obtained from (1))

GF Vertical AB Company

∴GF//CD