Can a Trigonometric Equation Be Solved Algebraically?

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Discussion Overview

The discussion revolves around the solvability of a trigonometric equation of the form A*cos(B*t) + sin(B*t)*(C-t) - D = 0, where t is the unknown variable. Participants explore whether this equation can be solved algebraically or if numerical methods are required, with references to intersections between sine and linear functions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Mike presents an equation involving trigonometric functions and seeks a solution for t.
  • One participant asserts that without specific numerical values for constants A, B, C, and D, the equation cannot be solved for t.
  • Mike questions the possibility of approximating the solution and discusses the intersection of a sine function and a linear function, noting a known intersection point.
  • Another participant challenges the assertion that a linear function can intersect a sine function in exactly two points.
  • Mike acknowledges the existence of a third intersection point but emphasizes that it is not relevant to his inquiry.
  • A participant provides an example of a linear function intersecting a sine function, demonstrating the use of arcsine to find solutions, but concludes that Mike's original equation may not be solvable algebraically and suggests numerical methods instead.

Areas of Agreement / Disagreement

Participants express differing views on the number of intersection points between sine and linear functions, with some asserting that there can be three points while others contest this. The discussion remains unresolved regarding the algebraic solvability of Mike's equation.

Contextual Notes

Participants note the importance of specific numerical values for constants in determining solvability and highlight the potential need for numerical methods, indicating limitations in the algebraic approach.

mike133
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Hi,
I wolud like to solve the folowing equation:
A*cos(B*t)+sin(B*t)*(C-t)-D=0 (t is unknown)
It is urgent.
Thanks in advance.
Regards
Mike
 
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Unless you have specific numerical values for at least some of the constants A, B, C, and D, this isn't solvable for t. Sorry.
 
Huh... is it possible to make an approxiamtion?

I would like to calculate the intersection between a sine function and a linear function. A sine function is of a form: y=A*sin(x). A linear function intersects sine function in two points. The first one (P1(pi,0)) is known, but we do not know the other one. We know an area between the x-axis and the sine + linear functios (look at the sketch). After integration we get an equation form the first post.
Regards,
Mike
 
Well you have a problem here, then, because a linear function CAN'T intersect a sine function in exactly two points.
 
Yes, they intersect in 3 points, but the third point is not important for me. I am not sure if you can see the sketch, I am sure I attached it, but I cannot see it.
 

Attachments

You have not specified the linear equation
So let's take a simple example

y=0.5 intersecting y=sin x
So we have
sin x = 0.5
Take the arcsine of both sides.
x = arcsine 0.5
Which yields pi/6 and 5pi/6 for 0 < x < 2pi

Similar approach should work for any linear equation y = mx + b

Edit in;
Looking at your equation above, you may not be able to solve it
algebraically. You may need to do it numerically.
A graphing calculator will be a big help.
It simply pick hundreds of values for t and calculates what that
gives for the equation and locates where the value is zero.
Just brute force math.
 

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