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If 90 < x < 135, then which of the following must be correct?
1. tan x < cos x
2. sin x < cos x
3. tan x < sin x
The answer is 1 & 3. And I want to know why option 1 must be correct. Is there any algebraic method that can be used to calculate this?
Brief answers are okay.
basic trigonometry
2012-07-02 1:51 am
回答 (1)
2012-07-02 1:59 am
✔ 最佳答案
1 tan x is increased from minus infinity to -1cos x is decreased from 0 to √ 2/2
So, (1) should be true
2 sin x is positive and cos x is negative
(2) should be false
3 tan x is increased from minus infinity to -1
sin x is decreased from 1 to √ 2/2
(3) should be true
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