what do they mean by
0<|x|< pi/2 ?
absolute function ( |y| )is confusing?
math. trigonometry.?
回答 (6)
2017-08-20 1:29 pm
Definition of |x| is:
When x ≥ 0: |x| = x
When x < 0: |x| = -x
Consider that 0 < |x| < π/2
When x ≥ 0:
0 < x < π/2
When x < 0:
0 < -x < π/2
Then, -π/2 < x < 0
Hence, 0 < |x| < π/2 is equivalent to (0 < x < π/2) or (-π/2 < x < 0)
OR: 0 < |x| < π/2 is equivalent to (-π/2 < x < π/2) but x ≠ 0
When x ≥ 0: |x| = x
When x < 0: |x| = -x
Consider that 0 < |x| < π/2
When x ≥ 0:
0 < x < π/2
When x < 0:
0 < -x < π/2
Then, -π/2 < x < 0
Hence, 0 < |x| < π/2 is equivalent to (0 < x < π/2) or (-π/2 < x < 0)
OR: 0 < |x| < π/2 is equivalent to (-π/2 < x < π/2) but x ≠ 0
2017-08-20 2:44 pm
Absolute value is always a positive number, in this case they also said it must be greater than 0.
2017-08-20 2:09 pm
0<x<π/2 or
0<-x<π/2
0>x>-π/2
x is in Quadrant 1 or 4
x ≠ 0
0<-x<π/2
0>x>-π/2
x is in Quadrant 1 or 4
x ≠ 0
2017-08-20 9:33 pm
-pi/2 < x < pi/2 and x > 0
It means x > 0 and x < pi/2
Quadrant I
It means x > 0 and x < pi/2
Quadrant I
2017-08-20 4:37 pm
x lies in first quadrant.
2017-08-20 1:38 pm
|y| is absolute value.
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