when x=1.2 find y
y=2tan x - tan2x
咁就姐係=2sec^2 x - 2sec^2 2x 啦
咁sec^2 點按計數機計呢???
唔識用計數機計 sec^2
2006-12-31 10:44 am
回答 (1)
2006-12-31 11:00 am
✔ 最佳答案
sec x = 1/cos x例如用計數機按sec² 30, 可以先按cos 30, 按 x², 然後再按 x^(-1), 便可得出答案.
但是y=2tan x - tan2x不等於2sec^2 x - 2sec^2 2x.
y = 2 tan x - tan 2x
= 2 tan x - (2 tan x)/(1-tan² x)
= 2 tan x [1 - 1/(1-tan²x)]
= 2 tan x [(- tan²x)/(1-tan²x)]
= -2 tan³x/(1-tan²x)
x = 1.2 radian?
y = 6.06
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