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Mathematics
Mathematics
Problem
Prove that
(
cos
α
+
cos
β
)
2
+
(
sin
α
+
sin
β
)
2
=
4
cos
2
(
α
−
β
2
)
.
(\cos \alpha + \cos \beta)^2 + (\sin \alpha + \sin \beta)^2 = 4 \cos^2 \left( \frac{\alpha - \beta}{2} \right).
(
cos
α
+
cos
β
)
2
+
(
sin
α
+
sin
β
)
2
=
4
cos
2
(
2
α
−
β
)
.
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