cosb.cos(2a – b) = cos square a - sin square (a - b)
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Answer:
sorry bro can't understand cos and ext
plz mark as brainlaist
Answered by
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Answer:
L.H.S=cos
2
A+cos
2
B−2cosAcosBcos(A+B)
=cos
2
A+cos
2
B−2cosAcosB(cosAcosB−sinAsinB)
=cos
2
A+cos
2
B−2cos
2
Acos
2
B+2cosAsinAcosBsinB
R.H.S=sin
2
(A+B)
=(sin(A+B))
2
=(sinAcosB+cosAsinB)
2
=sin
2
Acos
2
B+cos
2
Asin
2
B+2sinAcosAsinBcosB
=(1−cos
2
A)cos
2
B+cos
2
A−cos
2
Acos
2
B
=cos
2
B−cos
2
A+cos
2
B+cos
2
A−cos
2
Acos
2
B.
=cos
2
A+cos
2
B−2cos
2
Acos
2
B+2cosAsinAcosBSinB
Hence,
L.H.S=R.H.S
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