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Mathematics
Problem
For any function
f
:
A
→
B
f:A\to B
f
:
A
→
B
and the identity function
I
A
I_A
I
A
on
A
A
A
,
(
f
∘
I
A
)
(
x
)
(f\circ I_A)(x)
(
f
∘
I
A
)
(
x
)
is equal to a)
f
(
f
(
x
)
)
f(f(x))
f
(
f
(
x
))
b)
x
x
x
c)
f
(
x
)
f(x)
f
(
x
)
d)
I
A
(
f
(
x
)
)
I_A(f(x))
I
A
(
f
(
x
))
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