已知角a的终边过点p（-1,2）求sin(a x/2)的值求(sin^2a 3sinacosa-cos^2a)/(2sin^2a _数学解答

已知角a的终边过点p（-1,2）求sin(a x/2)的值求(sin^2a 3sinacosa-cos^2a)/(2sin^2a cos^2a)的值
救急，请快

人气：428 ℃　时间：2020-05-22 00:15:45

解答

cosa=-√5/5
tana=-2
sin(a/2)=±√[(5+√5)/10]
(sin²a+3sinacosa-cos²a)/(2sin²a+cos²a)=(tan²a+3tana-1)/(2tan²a+1)=1