(T=派)1.已知a属于[5T/2,7T/2],则根号下(1+sina)+根号下(1-sina)2.若1/cosa-1/sina=_数学解答

(T=派)1.已知a属于[5T/2,7T/2],则根号下(1+sina)+根号下(1-sina)
2.若1/cosa-1/sina=1 则 sin(2a)=

人气：404 ℃　时间：2020-06-29 20:32:48

解答

1
1+sina=(sin(a/2))^2+(cos(a/2))^2+2sin(a/2)cos(a/2)
=(sin(a/2)+cos(a/2))^2
所以
原式=|sin(a/2)+cos(a/2)|+|sin(a/2)-cos(a/2)|
=-sin(a/2)-cos(a/2)-sin(a/2)+cos(a/2)
=-2sin(a/2)
(因为5Pi/4