Trig Equation: Solving for Theta with Tangent and Sine Functions

  • Thread starter lylos
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In summary, using trigonometric identities, we can solve the equation Tan[60 degrees]=Sin[theta]/(1/3+Cos[theta]) by first rearranging it to (1/3+Cos[theta])Tan[60 degrees]=Sin[theta] and then using the Pythagorean identity to express sin(theta) in terms of cos(theta). This leads to the solution of 1.34004 radians or 76.7786 degrees.
  • #1
lylos
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Homework Statement


Tan[60 degrees]=Sin[theta]/(1/3+Cos[theta])


Homework Equations


Trig identities?


The Attempt at a Solution


Tan[60 degrees]=Sin[theta]/(1/3+Cos[theta])
(1/3+Cos[theta])Tan[60 degrees]=Sin[theta]
1/3 Tan[60 degrees]=Sin[theta]-Tan[60 degrees]*Sin[theta]

Now I'm lost...
I can put it in mathematica, and get a solution of 1.34004 Radians or 76.7786 degrees. I just don't know how to solve it!
 
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  • #2
lylos said:

The Attempt at a Solution


Tan[60 degrees]=Sin[theta]/(1/3+Cos[theta])
(1/3+Cos[theta])Tan[60 degrees]=Sin[theta]

OK so far.

1/3 Tan[60 degrees]=Sin[theta]-Tan[60 degrees]*Sin[theta]

The line is wrong. Your cosine morphed into a sine, so you'll need to fix that. I would actually back up to the previous line, leaving the cosine and sine on different sides. Look at [itex]\sin(\theta)[/itex] on the right side. Use a Pythagorean identity to express it in terms of [itex]\cos(\theta)[/itex].
 
  • #3
Thank you, I was able to get to the solution!
 

What is a trigonometric equation?

A trigonometric equation is an equation that involves one or more trigonometric functions, such as sin, cos, tan, sec, csc, or cot. These equations are used to solve for unknown angles or sides in a triangle, using the relationships between the sides and angles in a triangle.

How do I solve a trigonometric equation?

To solve a trigonometric equation, you need to isolate the variable (usually an angle) on one side of the equation. Then, use the inverse trigonometric functions (such as arcsin, arccos, or arctan) to find the value of the angle. Lastly, check your solution by plugging it back into the original equation.

What are the common trigonometric identities used to solve equations?

The most commonly used trigonometric identities are the Pythagorean identities (sin^2x + cos^2x = 1 and tan^2x + 1 = sec^2x), the double angle identities (sin2x = 2sinx cosx and cos2x = cos^2x - sin^2x), and the half angle identities (sin(x/2) = ±√[(1-cosx)/2] and cos(x/2) = ±√[(1+cosx)/2]).

What are some tips for solving tricky trigonometric equations?

Some tips for solving tricky trigonometric equations include: using the unit circle to determine the values of trigonometric functions at common angles, using trigonometric identities to rewrite the equation in a simpler form, and checking for extraneous solutions (solutions that do not satisfy the original equation).

How can I check my solution to a trigonometric equation?

You can check your solution to a trigonometric equation by plugging it back into the original equation and simplifying both sides. If the resulting equation is true, then your solution is correct. You can also graph both sides of the equation and see if they intersect at the value you found for the variable.

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