標題:
[Core]
F4 Math - Trigonometry (1)
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作者:
Steven2011
時間:
2011-7-24 04:18 PM
標題:
F4 Math - Trigonometry (1)
1a)求證sin(x-270度)= cos x 是恆等
睇象限?
1b)由此化簡,,,sinx cos(90度-x) – ( sin( x-270度)cos(180-x) )
2)試用sin x 表示 ( 1 / (1+cosx) ) + ( 1 / (1-cos x) )
3)己知tan x+ tan(90-x) =3 ,,求tan^2 x + ( 1 / tan^2 x )
點解唔係就甘2次==
4)己知sinx +coxx = k ,,用k表示 sinxcosx
5)COSX ( 3sinx+2) = 0
唔係甘做咩 COSX = 1 / (SINX+2)
SINX / COS X = 1/2咩
作者:
夏娜醬大好
時間:
2011-7-24 04:41 PM
1.
(a) 你可以靠睇
亦可以做:
sin(x-270) = sin(x+90) = sin(180-x-90) = sin(90-x) = cosx
(b) sin(x)cos(90-x) - sin(x-270)cos(180-x)
= (sinx)^2 + (cosx)^2
= 1
2.
1/(1+cosx) + 1/(1-cosx)
= (1-cosx+1+cosx)/[1-(cosx)^2]
= 2/(sinx)^2
3.
tanx+tan(90-x) = 3
tanx+1/tanx = 3
(tanx)^2+1/(tanx)^2
= (tanx)^2+1/(tanx)^2 +2-2
= (tanx+1/tanx)^2 -2
= 3^2 -2
= 7
4.
sinx+cosx = k
(sinx)^2+(cosx)^2+2sinxcosx = k^2
1+2sinxcosx = k^2
sinxcosx = (1/2)(k^2-1)
5.
cosx(3sinx+2) = 0
cosx = 0 or 3sinx+2 = 0
cosx = 0 or sinx = -2/3
作者:
Steven2011
時間:
2011-8-7 02:14 PM
THX YOU SO MUCH
= (tanx)^2+1/(tanx)^2 +2-2
= (tanx+1/tanx)^2 -2 <<<<<<WHY仲有2 GE 唔係2-2 =0 唔明= =
作者:
夏娜醬大好
時間:
2011-8-7 02:27 PM
Note that (tanx)^2+1/(tanx)^2 +2 = (tanx+1/tanx)^2
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