1°=60′,1′=60″; 故45″=0.75′; 23.75′=0.396°;所以58°23′45″=58.396°
25°18′+65°56′=90°74′=91°14′;
180°-(25°18′+65°56′)=179°60′-91°14′=88°46′
12°35′25″×4-20°20′15″=48°140′100″-20°20′15″=50°21′40″-20°20′15″=30°1′25″
98°12′25″÷5=95°192′25″÷5=95°190′145″÷5=19°38′29″
(98°12′25″÷5+20°5′16″)×2
=(19°38′29″+20°5′16″)×2
=39°43′45″×2=78°86′90″=79°27′30″