Why must x be acute for the identity \sqrt{\frac{1-\sin x}{1+\sin

Tori Hines

Tori Hines

Answered question


Why must x be acute for the identity 1sinx1+sinx=secxtanx to hold true?

Answer & Explanation



Beginner2022-01-25Added 15 answers

The first quadrant is 0x90 and the fourth quadrant is 270x360 or this is the same as 90x0. That is
represents both the first and the fourth quadrant.


Beginner2022-01-26Added 7 answers

The important point is that “identity” is true only when 90<x<90.
In another word, it is not true when the terminal arm falls in QII and QIII.
Note that the angle lies in 90<x<0 is also an acute angle, because the minus sign only refers to moving the terminal arm in the clockwise direction. The resultant angle is still acute.
Added: To move the terminal arm through 330 in the anticlockwise direction is the same as moving it through 30 in the clockwise direction.

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