Simplifying ANOTHER very anoying equation

  • Thread starter Titandwedebil
  • Start date
  • Tags
    Simplifying
I'll just add that you should note that (sin(2x))^2 = (2 sin(x) cos(x))^2 = 4 (sin(x))^2 (cos(x))^2, and likewise for (cos(2x))^2. Then (sin(2x))^2 + (cos(2x))^2 = 4 (sin(x))^2 (cos(x))^2 + 4 (sin(x))^2 (cos(x))^2 = 8 (sin(x))^2 (cos(x))^2. So you're almost there!
  • #1
Titandwedebil
20
0

Homework Statement


(cos4x) + 2(cos2x)(sin2x) + (sin4x)


Homework Equations


All Pythagorean, reciprocal, and quotient identities.


The Attempt at a Solution


Okay, so I thought that maybe (cos4x) + (sin4x) might be the same as its Pythagorean identity (which would make that mess just "1"; giving me...

2(cos2x)(sin2x) + 1

From there I haven't the slightest idea on what to do. The answer to this one is supposed to be just "1".
 
Physics news on Phys.org
  • #3
What's that?
 
  • #4
Well, (a+b)^2 = a^2 +b^2 + 2ab. I think this algebraic identity could be useful...Oh, and 1^2 =1.
 
  • #5
Titandwedebil said:
Okay, so I thought that maybe (cos4x) + (sin4x) might be the same as its Pythagorean identity (which would make that mess just "1"

No, that's not right. Just because
[tex]\cos^2 \theta + \sin^2 \theta = 1[/tex]
doesn't necessarily mean that
[tex]\cos^4 \theta + \sin^4 \theta = 1[/tex]
.

dextercioby said:
Think of (a+b)^2 expansion...
Titandwedebil said:
What's that?

We call this the "Square of a Binomial Pattern," typically learned in high school algebra.
 
  • #6
Titandwedebil said:

Homework Statement


(cos4x) + 2(cos2x)(sin2x) + (sin4x)


Homework Equations


All Pythagorean, reciprocal, and quotient identities.


The Attempt at a Solution


Okay, so I thought that maybe (cos4x) + (sin4x) might be the same as its Pythagorean identity (which would make that mess just "1"; giving me...

2(cos2x)(sin2x) + 1

From there I haven't the slightest idea on what to do. The answer to this one is supposed to be just "1".

Write s = sin(x) and note that cos^2(x) = 1-s^2, so you have (1-s^2)^2 + 2*(1-s^2)*s^2 + s^4. Expand it out.

RGV
 
  • #7
Ray Vickson said:
Write s = sin(x) and note that cos^2(x) = 1-s^2, so you have (1-s^2)^2 + 2*(1-s^2)*s^2 + s^4. Expand it out.

RGV
That looks like the hard way to do it! DexterCioby's idea is best.
 

Related to Simplifying ANOTHER very anoying equation

1. Why is it important to simplify equations?

Simplifying equations allows us to better understand the relationships between different variables and to solve problems more efficiently. It also makes the equation easier to work with and reduces the chances of making errors.

2. How do I know when an equation can be simplified?

An equation can be simplified when there are terms that can be combined or canceled out, and when the equation can be written in a more compact and organized form. This usually involves using the rules of algebra, such as the distributive property, to simplify the equation.

3. What are some common techniques for simplifying equations?

Some common techniques for simplifying equations include factoring, combining like terms, using the distributive property, and canceling out common factors. It is also helpful to have a good understanding of basic algebraic operations and their properties.

4. Can simplifying an equation change its solution?

No, simplifying an equation does not change its solution. Simplifying only involves rearranging and organizing the terms in the equation, but the overall value of the equation remains the same. Therefore, the solution to the simplified equation will be the same as the solution to the original equation.

5. Are there any rules or guidelines for simplifying equations?

Yes, there are some general rules and guidelines for simplifying equations, such as always working in the correct order of operations, being careful with negative signs, and checking for common factors. It is also important to pay attention to any restrictions or special cases that may apply to the equation.

Similar threads

  • Precalculus Mathematics Homework Help
Replies
3
Views
1K
  • Precalculus Mathematics Homework Help
Replies
31
Views
6K
  • Precalculus Mathematics Homework Help
Replies
4
Views
3K
  • Precalculus Mathematics Homework Help
Replies
6
Views
2K
  • Precalculus Mathematics Homework Help
Replies
3
Views
2K
  • Precalculus Mathematics Homework Help
Replies
9
Views
5K
  • Precalculus Mathematics Homework Help
Replies
6
Views
7K
  • Calculus and Beyond Homework Help
Replies
2
Views
1K
  • Precalculus Mathematics Homework Help
Replies
1
Views
2K
  • Calculus and Beyond Homework Help
Replies
6
Views
1K
Back
Top