Reducing a System of Equations to One Variable

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Discussion Overview

The discussion revolves around solving a system of equations involving three equations with two variables, aiming to reduce it to a single variable. The context includes mathematical reasoning and problem-solving strategies related to algebraic manipulation.

Discussion Character

  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant expresses difficulty in solving the system of equations and seeks guidance on reducing it to one variable.
  • Another participant suggests that Equation 3 allows for defining x2 in terms of x1 and that Equation 2 can define angle a in terms of x1 using arcsin, leading to a single-variable equation when substituted into Equation 1.
  • A different participant notes that the cos(arcsin()) expression can be simplified, implying a potential simplification in the solution process.
  • Another suggestion involves substituting x1 from Equation 2 into Equations 1 and 3, solving for x2, and equating the results to find angle a.
  • One participant proposes solving the first equation for x1 cos(a), squaring it, and adding it to the squared second equation to substitute into the third equation, ultimately reducing the number of unknowns.

Areas of Agreement / Disagreement

Participants present various methods for reducing the system to one variable, but there is no consensus on a single approach or solution. Multiple strategies are proposed, indicating differing views on the best method to achieve the goal.

Contextual Notes

Some participants' suggestions depend on the simplification of trigonometric identities and the manipulation of equations, which may involve assumptions about the relationships between the variables.

st3dent
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Hello, I am difficulty solving this system of equations.

Eqn1: 1.0416*10-21 = 4.75*10-27(x2) + 1.68*10-27(x1)(cos a)

Eqn2: 2.827 = (x1)(sin a)

Eqn3: 3.22896*10-16 = 8.4*10-28(x2)2 + 3.36*10-27(x1)2

I keep on getting equations with two variables in it. Can someone tell me how to get an eqn with only one variable out of this system.. Thanks!
 
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st3dent said:
Hello, I am difficulty solving this system of equations.

Eqn1: 1.0416*10-21 = 4.75*10-27(x2) + 1.68*10-27(x1)(cos a)

Eqn2: 2.827 = (x1)(sin a)

Eqn3: 3.22896*10-16 = 8.4*10-28(x2)2 + 3.36*10-27(x1)2

I keep on getting equations with two variables in it. Can someone tell me how to get an eqn with only one variable out of this system.. Thanks!

Eq 3 let's you define x_2 in terms of x_1 as a simple ratio. Eq 2 let's you define a in terms ofx_1 using an arcsin. Substituting these into Eq 1 will give you an equation with only one variable, although it will contain the cos of an arcsin.

Does that help?
 
st3dent,

The cos(arcsin( )) in the solution that Bob3141592 showed you how to get can be simplified.
 
Eq 2 gives you 'x_1 = 2.827/sin(a)'. Substitute this for x_1 in Eq 1 and 3, then in each solve for x_2 and equate. Can then calc 'a' and work back.
 
solve the first equation for x_1 cos(a), square, then add to the second equation squared. Substitute into the third equation for x_1^2, you only have one unknown then...backsubstitute...
 
Thank you.
 

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