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solve the equation cos(x)^2−sin(x)^2=sin(x) given on the domain [0,2pi) .

User JMax
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5 votes

Answer:

x = arccos(sqrt((1 + sin(x))/2)) + 2npi or x = pi - arccos(sqrt((1 + sin(x))/2)) + 2npi

Explanation:

cos^2(x) - sin^2(x) = sin(x) can be rewritten as cos^2(x) = sin^2(x) + sin(x)

Using the identity sin^2(x) + cos^2(x) = 1, we can simplify the equation as

cos^2(x) = 1 - cos^2(x) + sin(x)

Solving for cos^2(x), we get

cos^2(x) = (1 + sin(x))/2

Therefore, cos(x) = sqrt((1 + sin(x))/2) or cos(x) = -sqrt((1 + sin(x))/2)

To find the possible values of x, we need to find the values of sin(x) that satisfy this equation.

For the domain [0, 2pi), the range of sin(x) is [-1, 1], so we have:

cos(x) = sqrt((1 + sin(x))/2) for -1 <= sin(x) < 1

cos(x) = -sqrt((1 + sin(x))/2) for -1 <= sin(x) < 1

So, the solution is

x = arccos(sqrt((1 + sin(x))/2)) + 2npi or x = pi - arccos(sqrt((1 + sin(x))/2)) + 2npi

where n is an integer.

User Fan Jin
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