If you would have picked the minus, you would have found a different phase Angle, but you can't pick minus.

如果你要取负值，你会找到不同的，相角，但是你不能取负。

youdao

The angle actually goes from minus pi over two to pi over two.

实际上，角度取值范围是从-π/2到π

youdao

Main outcome measures were disc compression, defined as post - minus preloading disc height, and lumbar asymmetry, defined as the coronal Cobb Angle between the superior endplates of S1 and L1.

用椎间盘后减载预负荷高度、腰椎不对称度和L1、S1上终板之间冠状面cobb角来定义主要的测量结果，即椎间盘压缩程度。

youdao

I'm using the fact that when you take a cosine and change the angle inside the cosine, it doesn't care. whereas, if you go to the sine and change the angle inside the sine, it becomes minus sine.

我用了一个结论,当你使用余弦函数时,改变角度的正负,函数值不变,而对于正弦函数,改变角度的符号,则函数值也会变号

耶鲁公开课 - 基础物理课程节选

Production is being handled by 3ality Digital, previously responsible for the BCS game that turned some of our preconceived notions about 3D with its BCS National Championship broadcast a little over a year ago, which plans to use 5 cameras from a lower angle than usual to resemble the perspective of the actual players -- minus concussion-inducing blindside hits to the head.

ENGADGET: Cablevision bumps Comcast to the back, 3D sports at home starts next week