由 Searchtruth 於 星期四 六月 12, 2003 7:45 pm
抱歉~前面我算錯ㄌ...
=>(cosa+sina)/(cosa-sina)=(cosa+sina)
=>(cosa+sina)/(cosa-sina) - (cosa+sina) = 0
=>(cosa+sina)[1/(cosa-sina) -1 ] = 0
=>(cosa+sina)=0 , or 1/(cosa-sina) -1 =0
=>(i)cosa = - sina , or (ii)cosa-sina=1
(i):
a=3pi/4+kpi , 其中 k E Z
(ii):
cosa=sina+1
=>cos2a=sin2a+2sina+1
=>1-sin2a=sin2a+2sina+1
=>2sin2a+2sina=0
=>sina(sina+1)=0
=>sina=0 ,or sina=-1
=>cosa=0+1 , or -1+1
=>(sina=0,cosa=1),or(sina=-1,cosa=0)
=>a=2kpi ,or 3pi/2+2kpi , 其中 k E Z
由(i),(ii)
=>a=3pi/4+kpi , or 2kpi , or 3pi/2+2kpi , 其中 k E Z