(6sin a+5cos a)/(5cos a+3sin a)
={(6sin a+5cos a)/sina}/{(5cos a+3sin a)/sina}
=[6+5ctga]/[5ctga+3]=8
得出ctga=-18/35
ctga=1/tga=-35/18
(6sin a+5cos a)/(5cos a+3sin a)
={(6sin a+5cos a)/sina}/{(5cos a+3sin a)/sina}
=[6+5ctga]/[5ctga+3]=8
得出ctga=-18/35
ctga=1/tga=-35/18