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Originally Posted by micky1up
sins in your head using clock face rule
imagine a clock
10mins past = 1/6th
15mins past -=1/4
20 past= 1/3
30 mins past easy = 1/2
40 =2/3
anything over 45 add 25 and call it a percentage
so distance of track atb 50 at 10000= 50 +25(over 45 add 25)call at percentage 75% dot =7500yds
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Another (equivalent) way to estimate sines is:
sin(X degrees) = X / 60
which works surprisingly well for X < about 45 degrees.