sin1里的1是弧度,sin90度与sinπ/2相同,而π约等3.14,π/2大于1,所以sin90度大,
sin(1) = 0.8414709848079
sin(2) = 0.90929742682568
sin(3) = 0.14112000805987
sin(4) = -0.75680249530793