# Integral of cos^2 2x

**Cos2x** is one of the important trigonometric identities used in trigonometry khổng lồ find the value of the cosine trigonometric function for double angles. It is also called a double angle identity of the cosine function. The identity of cos2x helps in representing the cosine of a compound angle 2x in terms of sine and cosine trigonometric functions, in terms of cosine function only, in terms of sine function only, and in terms of tangent function only.

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Cos2x identity can be derived using different trigonometric identities. Let us understand the cos2x formula in terms of different trigonometric functions và its derivation in detail in the following sections. Also, we will explore the concept of cos^2x (cos square x) và its formula in this article.

1. | What is Cos2x? |

2. | What is Cos2x Formula in Trigonometry? |

3. | Derivation of Cos2x Using Angle Addition Formula |

4. | Cos2x In Terms of sin x |

5. | Cos2x In Terms of cos x |

6. | Cos2x In Terms of rã x |

7. | Cos^2x (Cos Square x) |

8. Xem thêm: Tổng Hợp Bài Văn Mẫu Tập Làm Văn Số 6 Lớp 7 Hay Nhất, Viết Bài Tập Làm Văn Số 6 Lớp 7 Đề 5 | Cos^2x Formula |

9. | How khổng lồ Apply Cos2x Identity? |

10. | FAQs on Cos2x |

Cos2x is an important trigonometric function that is used khổng lồ find the value of the cosine function for the compound angle 2x. We can express cos2x in terms of different trigonometric functions & each of its formulas is used to simplify complex trigonometric expressions & solve integration problems. Cos2x is a double angle trigonometric function that determines the value of cos when the angle x is doubled.

Cos2x is an important identity in trigonometry which can be expressed in different ways. It can be expressed in terms of different trigonometric functions such as sine, cosine, và tangent. Cos2x is one of the double angle trigonometric identities as the angle in consideration is a multiple of 2, that is, the double of x. Let us write the cos2x identity in different forms:

cos2x = cos2x - sin2xcos2x = 2cos2x - 1cos2x = 1 - 2sin2xcos2x = (1 - tan2x)/(1 + tan2x)We know that the cos2x formula can be expressed in four different forms. We will use the angle addition formula for the cosine function to derive the cos2x identity. Chú ý that the angle 2x can be written as 2x = x + x. Also, we know that cos (a + b) = cos a cos b - sin a sin b. We will use this lớn prove the identity for cos2x. Using the angle addition formula for cosine function, substitute a = b = x into the formula for cos (a + b).

cos2x = cos (x + x)

= cos x cos x - sin x sin x

= cos2x - sin2x

Hence, we have cos2x = cos2x - sin2x

Now, that we have derived cos2x = cos2x - sin2x, we will derive the formula for cos2x in terms of sine function only. We will use the trigonometry identity cos2x + sin2x = 1 lớn prove that cos2x = 1 - 2sin2x. We have,

cos2x = cos2x - sin2x

= (1 - sin2x) - sin2x

= 1 - sin2x - sin2x

= 1 - 2sin2x

Hence, we have cos2x = 1 - 2sin2x** **in terms of sin x.

Just lượt thích we derived cos2x = 1 - 2sin2x, we will derive cos2x in terms of cos x, that is, cos2x = 2cos2x - 1. We will use the trigonometry identities cos2x = cos2x - sin2x and cos2x + sin2x = 1 khổng lồ prove that cos2x = 2cos2x - 1. We have,

cos2x = cos2x - sin2x

= cos2x - (1 - cos2x)

= cos2x - 1 + cos2x

= 2cos2x - 1

Hence , we have cos2x = 2cos2x - 1 in terms of cosx

Now, that we have derived cos2x = cos2x - sin2x, we will derive cos2x in terms of chảy x. We will use a few trigonometric identities và trigonometric formulas such as cos2x = cos2x - sin2x, cos2x + sin2x = 1, and tan x = sin x/ cos x. We have,

cos2x = cos2x - sin2x

= (cos2x - sin2x)/1

= (cos2x - sin2x)/( cos2x + sin2x)

Divide the numerator and denominator of (cos2x - sin2x)/( cos2x + sin2x) by cos2x.

(cos2x - sin2x)/(cos2x + sin2x) = (cos2x/cos2x - sin2x/cos2x)/( cos2x/cos2x + sin2x/cos2x)

= (1 - tan2x)/(1 + tan2x)

Hence, we have cos2x = (1 - tan2x)/(1 + tan2x) in terms of tung x

Cos^2x is a trigonometric function that implies cos x whole squared. Cos square x can be expressed in different forms in terms of different trigonometric functions such as cosine function, và the sine function. We will use different trigonometric formulas và identities to lớn derive the formulas of cos^2x. In the next section, let us go through the formulas of cos^2x & their proofs.

To arrive at the formulas of cos^2x, we will use various trigonometric formulas. The first formula that we will use is sin^2x + cos^2x = 1 (Pythagorean identity). Using this formula, subtract sin^2x from both sides of the equation, we have sin^2x + cos^2x -sin^2x = 1 -sin^2x which implies cos^2x = 1 - sin^2x. Two trigonometric formulas that includes cos^2x are cos2x formulas given by cos2x = cos^2x - sin^2x và cos2x = 2cos^2x - 1. Using these formulas, we have cos^2x = cos2x + sin^2x & cos^2x = (cos2x + 1)/2. Therefore, the formulas of cos^2x are:

cos^2x = 1 - sin^2x ⇒ cos2x = 1 - sin2xcos^2x = cos2x + sin^2x ⇒ cos2x = cos2x + sin2xcos^2x = (cos2x + 1)/2 ⇒ cos2x = (cos2x + 1)/2Cos2x formula can be used for solving different math problems. Let us consider an example to understand the application of cos2x formula. We will determine the value of cos 120° using the cos2x identity. We know that cos2x = cos2x - sin2x & sin 60° = √3/2, cos 60° = 1/2. Since 2x = 120°, x = 60°. Therefore, we have

cos 120° = cos260° - sin260°

= (1/2)2 - (√3/2)2

= 1/4 - 3/4

= -1/2

**Important Notes on Cos 2x **

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**Example 2:** Express the cos2x formula in terms of cot x.

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**Solution:** We know that cos2x = (1 - tan2x)/(1 + tan2x) & tan x = 1/cot x

cos2x = (1 - tan2x)/(1 + tan2x)

= (1 - 1/cot2x)/(1 + 1/cot2x)

= (cot2x - 1)/(cot2x + 1)

**Answer:** Hence, cos2x = (cot2x - 1)/(cot2x + 1) in terms of cotangent function.

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