Solving Identity Question: (cosx)^2 = (1 + cos2x)/2

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In summary, the conversation discusses the identity equation (cosx)^2 = (1 + cos2x)/2, its purpose and steps to solve it, and tips for solving it. This equation is an identity, meaning it is true for all values of x, and its purpose is to practice using trigonometric identities. The steps to solve it involve expanding the right side using the double angle formula, simplifying and equating both sides, and checking solutions. The possible solutions are all real numbers, and some tips for solving it include familiarizing oneself with identities, expanding the right side before combining terms, and remembering to check solutions.
  • #1
ZedCar
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Homework Statement



In a worked example I have of an integration it states the integral of (cosx)^2 = the integral of (1 + cos2x)/2

How is this equality reached?

Is this a known identity, (cosx)^2 = (1 + cos2x)/2 ?

Thank you.


Homework Equations





The Attempt at a Solution

 
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  • #2
Yes.
 
  • #3
Yep, that's a very well-known identity, derived from very simple algebra from ##\cos\left(2\cdot x\right)=2\cdot\cos^2\left(x\right)-1##
 
  • #4
cos(x + x) = … ? :wink:
 

What is the identity equation in this problem?

The identity equation in this problem is (cosx)^2 = (1 + cos2x)/2. This is an identity equation because it is true for all values of x.

What is the purpose of solving this identity question?

The purpose of solving this identity question is to demonstrate the use of trigonometric identities and to practice solving equations involving trigonometric functions.

What are the steps to solve this identity question?

The steps to solve this identity question are:1. Expand the right side of the equation using the double angle formula for cosine.2. Combine like terms.3. Subtract (cosx)^2 from both sides of the equation.4. Simplify the left side of the equation.5. Divide both sides by 2.6. Take the square root of both sides.7. Simplify the right side of the equation.8. Set the two sides equal to each other to find the solutions for x.9. Check the solutions by plugging them back into the original equation.

What are the possible solutions for this identity question?

The possible solutions for this identity question are all real numbers, since the equation is an identity and is true for all values of x.

What are some tips for solving this identity question?

Some tips for solving this identity question are:- Familiarize yourself with trigonometric identities and their corresponding double angle formulas.- Make sure to expand the right side of the equation before combining like terms.- Remember to check your solutions by plugging them back into the original equation.- Keep in mind that this is an identity equation, so all values of x will be solutions.

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