Hi there!
We are given:
cos(7x)cos(4x) = -1 - sin(7x)sin(4x)
Begin by moving all terms with variables to one side:
cos(7x)cos(4x) + sin(7x)sin(4x) = -1
The corresponding trig identity is cos(A - B). Thus:
cos(7x - 4x) = cos(7x)cos(4x) + sin(7x)sin(4x) = -1
cos(3x) = -1
cos = -1 at π, so:
3x = π
x = π/3
We can also find another solution. Let 3π = -1:
3x = 3π
x = π
Thus, solutions on [0, 2π) are π/3 and π.
The most appropriate choice for unitary method will be given by-
Length of driveway in the drawing is 3 inch
What is unitary method?
Unitary method is the method in which value of a single unit can be calculated from the value of a multiple unit and value of a multiple unit can be calculated from the value of a single unit.
Sometimes value of single unit is less than value of multiple unit
For example - cost of food and quantity of food
Sometimes value of single unit is more than value of multiple unit
For example- Number of men and time taken by those men to do a work
Here,
Scale used by Maureen is 1 inch = 8ft
Actual length of house's driveway = 24 feet
8 ft of room is equal to 1 inch on scale
1 ft of room is equal to inch on scale
24 feet of room is equal to inch on scale
24 feet of room is equal to 3 inch on scale
Length of driveway in the drawing is 3 inch
To learn more about unitary method, refer to the link-
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