Mastering Trigonometric Identities: 3 Methods To Express Cosine Squared Of Angle 2X

cos2x=

cos^2x-sin^2x or 1-2sin^2x

The expression cos2x refers to the trigonometric function cosine squared of angle 2x. There are different ways to express this function using trigonometric identities. Here are some common ones:

1. Using the double angle formula for cosine:

cos2x = cos(2x) = cos^2(x) – sin^2(x)

This identity states that the cosine of twice an angle is equal to the difference between the squares of the cosine and sine of the angle.

2. Using the Pythagorean identity for sine and cosine:

cos2x = cos^2(x) – (1 – cos^2(x))

This identity follows from the fact that sin^2(x) + cos^2(x) = 1 for any angle x.

3. Using the identity cos2x = 2cos^2(x) – 1:

This identity can be derived by rewriting cos(2x) as cos(x + x), applying the sum formula, and simplifying.

All three of these expressions are equivalent and can be used interchangeably, depending on the context and the problem at hand.

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