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Mathematics
Mathematics
Problem
Which of the following is the correct identity for
cos
α
−
cos
β
\cos\alpha-\cos\beta\;
cos
α
−
cos
β
? a)
2
cos
α
+
β
2
cos
α
−
β
2
2\cos\dfrac{\alpha+\beta}{2}\,\cos\dfrac{\alpha-\beta}{2}
2
cos
2
α
+
β
cos
2
α
−
β
b)
2
sin
α
+
β
2
sin
α
−
β
2
2\sin\dfrac{\alpha+\beta}{2}\,\sin\dfrac{\alpha-\beta}{2}
2
sin
2
α
+
β
sin
2
α
−
β
c)
−
2
sin
α
+
β
2
sin
α
−
β
2
-2\sin\dfrac{\alpha+\beta}{2}\,\sin\dfrac{\alpha-\beta}{2}
−
2
sin
2
α
+
β
sin
2
α
−
β
d)
−
2
sin
α
+
β
2
cos
α
−
β
2
-2\sin\dfrac{\alpha+\beta}{2}\,\cos\dfrac{\alpha-\beta}{2}
−
2
sin
2
α
+
β
cos
2
α
−
β
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