✔ 最佳答案
好難睇,除可以用 '/'代表,#唔打都冇所謂,同埋有冇2) ga?
1) 1/cos^2 - 1 = (1-cos^2)/cos^2 = sin^2/cos^2 = tan^2
(since sin^2 + cos^2 = 1)
3)分母睇唔清楚,唔該補一補充,可能會錯
sin/ (1 - cos) = sin(1 + cos)/(1+cos)(1-cos) = sin(1 + cos)/(1 - cos^2)
= sin(1+cos)/sin^2 = (1 + cos)/sin = csc + cot
(csc = 1/sin , cot = 1/tan)
4) 1 + tan^2 = 1 + sin^2/cos^2 = (cos^2 + sin^2) / cos^2 = 1 / cos^2 = sec^2
(學左sec未? sec = 1 / cos)
2007-07-31 16:21:43 補充:
值?不知角,何來知值?簡化用的通常都只有代入公式,f.2常用的公式如下:sin x = cos (90 - x)tan x = 1/tan(90 - x)sin^2 cos^2 = 1sin / cos = tan第2種方法就是類似有理化的方法,就好像第3條,因為分母有 1 - cos x,你又應該知 (a b)(a - b) = a^2 - b^2 呢條式,而且1 - cos^2 可以化簡,所以就會分子同分母一齊乘(1 cos x),咁樣就可以將分母變做1 - cos^2
2007-07-31 16:22:20 補充:
打錯左d,唔係sin^2 cos^2 = 1係sin^2 + cos^2 = 1
2007-07-31 16:23:45 補充:
唔知點解第1次補充裡面個d + 唔見哂,打多次~值?不知角,何來知值?簡化用的通常都只有代入公式,f.2常用的公式如下:sin x = cos (90 - x)tan x = 1/tan(90 - x)sin^2 +cos^2 = 1sin / cos = tan第2種方法就是類似有理化的方法,就好像第3條,因為分母有 1 - cos x,你又應該知 (a + b)(a - b) = a^2 - b^2 呢條式,而且1 - cos^2 可以化簡,所以就會分子同分母一齊乘(1 + cos x),咁樣就可以將分母變做1 - cos^2