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Mathematics
Mathematics
Problem
If
cos
−
1
(
x
2
−
y
2
x
2
+
y
2
)
=
tan
−
1
a
\cos^{-1} \left( \frac{x^2 - y^2}{x^2 + y^2} \right) = \tan^{-1} a
cos
−
1
(
x
2
+
y
2
x
2
−
y
2
)
=
tan
−
1
a
, then prove that
d
y
d
x
=
y
x
\frac{dy}{dx} = \frac{y}{x}
d
x
d
y
=
x
y
.
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