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Tardigrade
Question
Mathematics
Find the derivative of (x2 + 1) cos x.
Q. Find the derivative of
(
x
2
+
1
)
cos
x
.
2214
246
Limits and Derivatives
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A
2
x
cos
x
−
(
x
2
+
1
)
s
in
x
51%
B
2
x
s
in
x
−
x
2
cos
x
21%
C
x
2
(
cos
x
−
s
in
x
)
17%
D
2
x
(
s
in
x
+
cos
x
)
11%
Solution:
Let
f
(
x
)
=
(
x
2
+
1
)
cos
x
∴
f
′
(
x
)
=
(
x
2
+
1
)
′
cos
x
+
(
cos
x
)
′
(
x
2
+
1
)
=
(
2
x
+
0
)
cos
x
+
(
−
s
in
x
)
(
x
2
+
1
)
=
2
x
cos
x
−
(
x
2
+
1
)
s
in
x