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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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Given the system of linear equations. x=y+3 y=-4x-3 Part A: Solve the linear system of equations by graphing Part B: Use substit
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Answer:

see below

Step-by-step explanation:

x=y+3

Subtract 3 from each side

x-3 = y

y = x-3

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We have both equations in slope intercept form

y = mx +b where m is the slope and b is the y intercept

graph is below

They both have the same y intercept so they intersect at (0,-3)

Substitution

x=y+3

y=-4x-3

Substitute the second equation into the first equation

x=y+3

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Add 4x to each side

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y = -4x-3

y = 0-3

y = -3

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Additon

x=y+3

Subtract y from each side

x-y = 3

y=-4x-3

Add 4x to each side

4x+y =-3

Add the equations together to eliminate y

x-y = 3

4x+y =-3

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5x +0y =0

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Find all sides of a right triangle whose perimeter is equal to 60 cm and its area is equal to 150 square cm
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Answer:

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Step-by-step explanation:

Let the sides of the right angle be x, y and h

x is the breadth

y is the height

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x + y +h  = 60

x+y = 60-h .... 1

If its area is equal to 150 square cm, then;

Area = 1/2 * base * height

Area = 1/2 *x * y

xy/2 = 150

xy = 300 ....2

According to pythagoras theorem;

x² + y² = h²

On expanding x² + y²

x² + y² = (x+y)² - 2xy

The equation becomes

(x+y)² - 2xy = h² ... 3

Substitute equation 1 and 2 into 3;

From 3;

(x+y)² - 2xy = h² ... 3

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Recall that x+y+h = 60

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Substitute 5 into 4;

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y = 20 and 15

since x+y = 35

x + 20 = 35

x = 35 - 20

x = 15

Hence the sides of the triangle are 15cm by 20cm by 25cm

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Step-by-step explanation:

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