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2 years ago

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

1 answer:

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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2 years ago

Evaluate g(x)=3x when x=−2,0, and 5. g(−2)= g(0)= g(5)=

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Answer:

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Step-by-step explanation:

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2 years ago

The International Business Club starts the school year with $250.50 in their account. They spend $35 each month on activities. T

svlad2 [7]

Answer:

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Step-by-step explanation:

Whenever an equation asks for when it will take x (or m in this case) amount of things or time you should know that there will be 2 different equations that have to equal each other

The equation will be 250.50 - 35m = 300 - 45.25m

The 35m is being subtracted from 250.50 because they are losing money each time they spend. This also applies to 45.25m

Also 35m and 45.25m are variables because it says they spend that much money each month. They don't specify how many months, so we have to put a variable after it.

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2 years ago

Hector has a floor plan showing his new house. On the floor plan, his bedroom is 3 inches wide and 3

Nat2105 [25]

Question:

Hector has a floor plan showing his new house. On the floor plan, his bedroom is 3 inches wide and 3 1/2 inches long. The scale of the floor plan is 1/4 inch = 1 foot. What is the actual length of Hector’s room?

Answer:

The actual length of Hector room is 14 foot

Solution:

Given that, On the floor plan, his bedroom is 3 inches wide and $3\frac{1}{2}$ inches long

The scale of floor plan is given as:

$\frac{1}{4} \text{ inch} = 1 \text{ foot }$

Therefore,

$1 \text{ inch } = 4 \text{ foot}$

To find: Actual length of floor

From given question,

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Converting the mixed fraction to improper fraction,

$length = \frac{2 \times 3 + 1}{2} = \frac{7}{2} \text{ inches }$

Since, 1 inch = 4 foot

$\frac{7}{2} \text{ inches } = \frac{7}{2} \times 4 \text{ foot } = 14 \text{ foot }$

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2 years ago

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Vsevolod [243]

Solution:

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8 0

2 years ago

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