cos (A-B) - cos(A + B)=
sin (A+B)-sin(A-B)=
sin (A+B)+sin(A-B)=
cos(A+B) + cos(A-B) =
a) 2 sin Acos B
b) 2 sin Asin B
c) 2 cos A.sinB
d) 2cos Acos B
Answers
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Answer:
Explanation:
using the
trigonometric identities
∙
x
sin
(
A
+
B
)
=
sin
A
cos
B
+
cos
A
sin
B
∙
x
sin
(
A
−
B
)
=
sin
A
cos
B
−
cos
A
sin
B
Adding the 2 equations gives
sin
(
A
+
B
)
+
sin
(
A
−
B
)
=
2
sin
A
cos
B
Subtracting the 2 equations gives
sin
(
A
+
B
)
−
sin
(
A
−
B
)
=
2
cos
A
sin
B
let
C
=
A
+
B
and
D
=
A
−
B
⇒
A
=
C
+
D
2
and
B
=
C
−
D
2
⇒
sin
C
+
sin
D
=
2
sin
(
C
+
D
2
)
cos
(
C
−
D
2
)
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