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Elden [556K]
3 years ago
5

Prove that sinA-sin3A+sin5A-sin7A/cosA-cos3A-cos5A+cos7A= cot2A

Mathematics
1 answer:
MAVERICK [17]3 years ago
4 0
Write the left side of the given expression as N/D, where
N = sinA - sin3A + sin5A - sin7A
D = cosA - cos3A - cos5A + cos7A
Therefore we want to show that N/D = cot2A.

We shall use these identities:
sin x - sin y = 2cos((x+y)/2)*sin((x-y)/2)
cos x - cos y = -2sin((x+y)/2)*sin((x-y)2)

N = -(sin7A - sinA) + sin5A - sin3A
    = -2cos4A*sin3A + 2cos4A*sinA
    = 2cos4A(sinA - sin3A)
    = 2cos4A*2cos(2A)sin(-A)
    = -4cos4A*cos2A*sinA

D = cos7A + cosA - (cos5A + cos3A)
   = 2cos4A*cos3A - 2cos4A*cosA
   = 2cos4A(cos3A - cosA)
   = 2cos4A*(-2)sin2A*sinA
   = -4cos4A*sin2A*sinA

Therefore
N/D = [-4cos4A*cos2A*sinA]/[-4cos4A*sin2A*sinA]
       = cos2A/sin2A
      = cot2A

This verifies the identity.
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<h3>What is Probability?</h3>

The area of mathematics known as probability deals with numerical descriptions of how likely it is for an event to happen or for a claim to be true. A number between 0 and 1 is the probability of an event, where, broadly speaking, 0 denotes the event's impossibility and 1 denotes its certainty.

According to the given information:

1) There are a total of 10 slips after adding.

8 slip with 3 on it

2 slips with 9  on it

 value = Probability of 3 x 3 plus Probability of 9 x 9.

=  (8 / 11)  x 3 + (2/ 11)  x 9

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2 )No of total slips after addition = 12

8 slip with 3 on it

4 slips with 9  on it

 value = Probability of 3 x 3 plus Probability of 9 x 9.

=  (8 / 12)  x 3 + (4 / 12)  x 9

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3 )Let n be the required number

No of total slips after addition = 10+n

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value = Probability of 3 x 3 plus Probability of 9 x 9.

=  (8 / 10+n )  x 3 + (2+n  / 10+n )  x 9 = 6

24 + 18 + 9n / 10 + n  = 6

42 + 9n = 60 + 6n

3 n = 18

n = 6

4 )Let n be the required number

No of total slips after addition = 10+n

8 slip with 3 on it

2 + n  slips with 9  on it

expectation value = probability of 3 x 3 + probability of 9 x 9

=  (8 / 10+n )  x 3 + (2+n  / 10+n )  x 9 = 8

24 + 18 + 9n / 10 + n  = 8

42 + 9n = 80 + 8n

n = 38

Minimum of 38 has to be added .

To know more about Probability visit:

brainly.com/question/17487084

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