若a∈(3/2π,2π) 且sinα=-12/13,求cosa,tana,cota,sin2a
问题描述:
若a∈(3/2π,2π) 且sinα=-12/13,求cosa,tana,cota,sin2a
答
sina=-12/13
a∈(3/2π,2π)
cosa=√1-sin^2a=5/13
tana=sina/cosa=-12/5
cota=1/tana=-5/12
sin2a=2sinacosa=-120/169