∫ 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