Question

Find the exact value of sin(2x) if sin(x)=-1/2.

Answer 1

Answer: The value of sin(2x) can be found using the identity:

sin(2x) = 2sin(x)cos(x)

Since sin(x) = -1/2, we can use the Pythagorean identity to find the value of cos(x):

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

So

cos^2(x) = 1 - sin^2(x) = 1 - (-1/2)^2 = 1 - 1/4 = 3/4

Taking the square root of both sides:

cos(x) = ± sqrt(3)/2

Since sin(x) is negative and cos(x) must be positive, we get:

cos(x) = sqrt(3)/2

Finally, substituting the values of sin(x) and cos(x) into the formula for sin(2x), we get:

sin(2x) = 2sin(x)cos(x) = 2 * (-1/2) * sqrt(3)/2 = -sqrt(3)

So the exact value of sin(2x) is -√(3).

Explanation: