viewing angle 41.8 x 80' + 5'5"=
viewing angle 41.8 x 80' + 5'5"= ?
41.8×80′+5′5"=41.8×80′+5′+5"=41.8×80′+5′+5"⋅1′60"=41.8×80′+5′+(560)′=3344′+5′+(560)′=3349′+(560)′=3349′⋅6060+(560)′=3349′⋅60+5′60=200945′60⋅1∘60′=(20094560⋅60)∘=55.8180ˉ5∘