13.abc = A= c #11 loga+b c+loga-b c = 2 ( loga+bc). (loga-bc) '
(2)等腰
(3)直角 (4)等腰直角
則此三角形的形狀為 (1)等邊
【解】:(3)
,
loga+b C+loga-b c = 2 ( loga+bc) · (loga-b c )
1
1
log (a+b) log(a - b)
2
【進階題】
Key
1
1
log(a+b) log (a - b)
logm n-logn m=1
2
(2010). Logelab)t (0g, (atb)
log,
Togc(atb)x log² (a+b) = logela+ble (oge(at)...
4
:: loge(a+b) + logela+b) = 2 · logo (a²b²) = 2 = log₁²
a²³b²³c²° ಳ²b²tc²
