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Sin(x/7)sin(x/7)=1/2(1-cos(2x/7)
OA. True
OB. False

User Malimo
by
2.3k points

2 Answers

6 votes
6 votes
Hi! The answer is B. False!

Hope this helps <3
User Rod Xavier
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20 votes
20 votes

Answer:

OA.True

Explanation:

is true

bcos if u multply sin(x/7)sin(x/7) u will have

sin²(x/7)

from trigonometry identity

sin²(x/7)+cos²(x/7)=1

sin²(x/7)=1-cos²(x/7)...............(1)

from trigonometry identity

cos(2x/7)=cos²(x/7) - sin²(x/7)

cos²(x/7)=cos(2x/7)+sin²(x/7) ........(2)

subtitue (2) in (1) we have

sin²(x/7)=1-(cos(2x/7)+sin²(x/7))

=1-cos(2x/7) - sin²(x/7)

sin²(x/7)+sin²(x/7)=1-cos(2x/7)

2sin²(x/7)=1-cos(2x/7)

sin²(x/7)=½(1-cos(2x/7)

sin(x/7)sin(x/7)=½(1-cos(2x/7))

User Alexander Bogushov
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3.1k points