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Mathematics
Problem
Prove that
tan
−
1
(
1
+
x
−
1
−
x
1
+
x
+
1
−
x
)
=
π
4
−
1
2
cos
−
1
x
\tan^{-1} \left( \frac{\sqrt{1+x} - \sqrt{1-x}}{\sqrt{1+x} + \sqrt{1-x}} \right) = \frac{\pi}{4} - \frac{1}{2} \cos^{-1} x
tan
−
1
(
1
+
x
+
1
−
x
1
+
x
−
1
−
x
)
=
4
π
−
2
1
cos
−
1
x
,
−
1
2
≤
x
≤
1
-\frac{1}{\sqrt{2}} \le x \le 1
−
2
1
≤
x
≤
1
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