Question

find the value of cos^2 13cos^2 47 +cos^2 73​

Answer 1

Answer:

L.H.S. =

2

1

[1 + cos 146

∘

+ 1 + 1 + cos 94

∘

+ cos 120

∘

+ cos 26

∘

]

=

2

1

[2−

2

1

+cos146

∘

+cos94

∘

+cos26

∘

]

4∵cos120

∘

=−

2

1

=

2

1

[

2

3

+cos146

∘

+2cos60

∘

cos34

∘

]

=

2

1

[

2

3

−cos34

∘

+cos34

∘

]=

4

3

.

Step-by-step explanation:

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