Why is this equation equal to another equation?

  • Thread starter mapa
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In summary, it is necessary to prove that one equation is equal to another in order to ensure that both equations accurately describe the relationship between variables. This can be done through algebraic manipulation or using mathematical properties. Two equations can be equal even if they appear different, as long as they represent the same relationship and can be transformed into each other. Understanding why equations are equal is important for a strong foundation in mathematics and has real-life applications in fields such as engineering, physics, and chemistry.
  • #1
mapa
29
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x = (2vsin(theta)cos(theta))/g = (vsin2(theta))/g

v = null velocity

x = distance

g = gravity

How is the first equation equal to the second one?
How the sin2(theta) come to be and where did the cos(theta) go?
 
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  • #2
Trigonometric identity:

[tex]2 \sin (\theta) \cos (\theta) = \sin (2 \theta)[/tex]
 
  • #3
thank you
 
  • #4
Nabeshin said:
Trigonometric identity:

[tex]2 \sin (\theta) \cos (\theta) = \sin (2 \theta)[/tex]

Or more generally, sin(A+B)=sin(A)cos(B)+cos(A)sin(B).
Also handy to know: cos(A+B)=cos(A)cos(B)-sin(A)sin(B).
 
  • #5


The first equation, x = (2vsin(theta)cos(theta))/g, can be simplified using the trigonometric identity sin2(theta) = 2sin(theta)cos(theta). This results in the second equation, x = (vsin2(theta))/g. The cos(theta) is no longer needed in the simplified equation because it is already accounted for in the sin2(theta) term. Essentially, the sin2(theta) term is a more concise way of representing the product of sin(theta) and cos(theta). Therefore, the two equations are equivalent and can be used interchangeably in calculations involving distance, velocity, and gravity.
 

1. Why is it necessary to prove that one equation is equal to another equation?

It is necessary to prove that one equation equals another because it ensures that both equations are describing the same relationship between variables. If one equation is not equal to another, it could lead to incorrect conclusions or solutions in mathematical problems.

2. How can I show that one equation is equal to another?

There are several ways to show that one equation is equal to another. One way is to use algebraic manipulation and operations to transform one equation into the other. Another way is to use mathematical properties, such as the commutative or associative property, to rearrange the terms of one equation to match the other.

3. Can two equations be equal even if they look different?

Yes, two equations can be equal even if they look different. As long as they represent the same relationship between variables and can be transformed into each other using algebraic or mathematical operations, they are equal. This is similar to how different words can have the same meaning.

4. Why is it important to understand why one equation is equal to another?

Understanding why one equation is equal to another is important because it helps to build a strong foundation in mathematics. It allows for a deeper understanding of mathematical concepts and relationships, and it can also aid in solving more complex problems that involve multiple equations.

5. What are some real-life applications of proving equations equal to each other?

Proving equations equal to each other has many real-life applications, such as in engineering, physics, and chemistry. For example, in engineering, understanding the relationship between force, mass, and acceleration can help in designing structures that can withstand certain forces. In physics, proving equations equal to each other can help in predicting the behavior of objects in motion. In chemistry, it can aid in determining the amount of reactants needed to produce a certain product in a chemical reaction.

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