{F.4 A.Math} Trigonometry

sin Ａ=2 tan Ａ
sin A = 2 sin A / cos A
sin A - 2 sin A / cos A = 0
sin A(1 - 2 / cos A)=0
sin A = 0 or cos A = 2 (reject)
A = 0 or pi or 2 pi
=0 or 3.14 or 6.28


2006-12-06 19:01:51 補充：
my answer is measured in RADIAN

sin Ａ=2 tan Ａ
sin Ａ-2 tan Ａ=0
sin Ａ(1-2/cosA)=0
sinA=0 or cosA=0.5
A=180N or A=360N+/-60 where N=0,1,2,3,...

sin A = 2 tan A
sin A = 2 * sin A / cos A
sin A * cos A = 2sinA (assume cos A not = zero)
sinAcosA-2sinA = 0
sinA ( cosA - 2) = 0
sinA = 0 or cos A = 2 (rejected because max.(cos A) = 1)
sin A = 0
A = arc sin 0
A = 0.0 degree (to nearest 0.1)