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Mathematics
Problem
In
△
D
E
F
\triangle DEF
△
D
E
F
,
∠
D
=
4
y
+
10
∘
\angle D = 4y + 10^{\circ}
∠
D
=
4
y
+
1
0
∘
,
∠
E
=
2
y
+
40
∘
\angle E = 2y + 40^{\circ}
∠
E
=
2
y
+
4
0
∘
and
∠
F
=
4
y
+
10
∘
\angle F = 4y + 10^{\circ}
∠
F
=
4
y
+
1
0
∘
. Which of the following is always true? a)
D
E
=
D
F
DE = DF
D
E
=
D
F
b)
D
E
=
E
F
DE = EF
D
E
=
E
F
c)
D
F
=
E
F
DF = EF
D
F
=
E
F
d)
D
E
=
D
F
=
E
F
DE = DF = EF
D
E
=
D
F
=
E
F
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