for the acute angles in a right triangle, sin(2x)=cos (4x+12 degree). what is the measure of the larger angle?

Answer 1

Let's solve the equation sin(2x) = cos(4x + 12) for the acute angles in the right triangle.

Using the identity sin(2x) = 2sin(x)cos(x) and cos(4x + 12) = cos(4x)cos(12) - sin(4x)sin(12), we can rewrite the equation as:

2sin(x)cos(x) = cos(4x)cos(12) - sin(4x)sin(12)

Expanding the right side of the equation using the identity cos(a + b) = cos(a)cos(b) - sin(a)sin(b), we have:

2sin(x)cos(x) = cos(4x)cos(12) - sin(4x)sin(12)
2sin(x)cos(x) = cos(4x - 12)

Now, let's use the identity cos(2x) = 1 - 2sin^2(x) to substitute for cos(4x):

2sin(x)cos(x) = 1 - 2sin^2(2x - 12)

Rearranging the equation and combining like terms, we get:

2sin^2(x) + 2sin(x)cos(x) - 1 = 0

Now, let's use the Pythagorean Identity sin^2(x) + cos^2(x) = 1 to substitute for sin^2(x):

2(1 - cos^2(x)) + 2sin(x)cos(x) - 1 = 0
2 - 2cos^2(x) + 2sin(x)cos(x) - 1 = 0
-2cos^2(x) + 2sin(x)cos(x) + 1 = 0

Now we have a quadratic equation in terms of cos(x). Let's solve it using the quadratic formula:

cos(x) = (-b ± √(b^2 - 4ac))/2a

a = -2, b = 2sin(x), c = 1

cos(x) = (-(2sin(x)) ± √((2sin(x))^2 - 4(-2)(1)))/(2(-2))
cos(x) = (-2sin(x) ± √(4sin^2(x) + 16))/(4)
cos(x) = (-sin(x) ± √(sin^2(x) + 4))/(2)

Since x is an acute angle, sin(x) cannot be negative. Therefore, we take the positive value of cos(x):

cos(x) = (-sin(x) + √(sin^2(x) + 4))/(2)

Now, let's substitute this expression for cos(x) back into the equation 2sin(x)cos(x) = 1 - 2sin^2(2x - 12):

2sin(x)((-sin(x) + √(sin^2(x) + 4))/(2)) = 1 - 2sin^2(2x - 12)
sin(x)((-sin(x) + √(sin^2(x) + 4))) = 1 - 2sin^2(2x - 12)

Expanding and simplifying the equation further, we get:

-sin^2(x) + sin(x)√(sin^2(x) + 4) = 1 - 2sin^2(2x - 12)
sin(x)√(sin^2(x) + 4) = sin^2(x) + 2sin^2(2x - 12) - 1

Square both sides of the equation to eliminate the square root:

sin^2(x)(sin^2(x) + 4) = (sin^2(x) + 2sin^2(2x - 12) - 1)^2

Expanding and simplifying the equation, we get:

sin^4(x) + 4sin^2(x) = sin^4(x) + 4sin^2(x) - 4sin^2(x) - 4 + 1

Simplifying further, we get:

sin^4(x) + 4sin^2(x) = -3

Since sin^4(x) is always non-negative, we can conclude that -3 is not possible as an answer. Therefore, there are no solutions to the equation and we cannot determine the measure of the larger angle.