How Do You Convert Sin and Cos Values to Tan in Trigonometry?

In summary, the problem involves converting the given angles (20° and 380°) to equivalent angles less than or equal to 90° in order to use trigonometric functions. The value of tan 200° is not the same as for sine and cosine due to the period of tangent. The reference angle for 380° is 20°, which can be used to simplify the expression to (sin 20° / cos 20°) + tan 200°. The reference angle for 200° is 20°, and with the simplification, the value of tan 200° can be easily determined.
  • #1
CrossFit415
160
0

Homework Statement



(sin 20° / cos 380°) + tan 200°


Homework Equations



tan = sin / cos



The Attempt at a Solution



Ok so.. I know tan = sin / cos. How do I convert sin 20° / cos 380° into tan? What should I do with the numbers? Thanks
 
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  • #2
Hi CrossFit415! :wink:

Trig tables only go up to 90° :cry:

… so they want you to convert all the angles to ≤ 90° ! :smile:
 
  • #3
What, someone actually uses tables to find trig values?

CrossFit415, what, exactly are you asked to do? If just find the value of that, why change anything, why not just put the numbers into a calculator? (Being sure it is in degree mode, of course.

(Yes, I see that 380= 360+ 20 but I don't see that that helps.)
 
  • #4
Yea but I can't use a calculator. I just wanted to know how to manually convert them. Thanks
 
  • #5
I'm assuming that we could leave the answer as a multiple or power of a trig function.

OP: you were told in one of your other threads what to do with coterminal angles. From what HallsofIvy post, you can see that
[tex]\frac{\sin 20^{\circ}}{\cos 380^{\circ}} + \tan 200^{\circ}[/tex]
[tex]= \frac{\sin 20^{\circ}}{\cos 20^{\circ}} + \tan 200^{\circ}[/tex]

Also, what can you do with tan 200°? (Hint: it's not the same as what can be done with sine and cosine, because the period of tangent is different.)
 
  • #6
What is the reference angle for 380 degrees? Think how that relates to the sin of 20 degrees and tan.

The value for tan should pop out at you!

Edit: Then think about what the reference angle for 200 degrees is.
 
Last edited:

1. What is the definition of a trigonometric equation?

A trigonometric equation is an equation that involves trigonometric functions, such as sine, cosine, or tangent, and one or more variables. These equations are used to solve for unknown angles or sides in a right triangle or to model periodic phenomena.

2. How do you solve a trigonometric equation?

To solve a trigonometric equation, you must first isolate the trigonometric function on one side of the equation. Then, use inverse trigonometric functions, such as arcsine, arccosine, or arctangent, to find the value of the variable. Finally, check your solution by plugging it back into the original equation.

3. What are the common trigonometric identities?

The most commonly used trigonometric identities are the Pythagorean identities, which include sin^2x + cos^2x = 1 and tan^2x + 1 = sec^2x. Other identities include the double angle identities, sum and difference identities, and product-to-sum identities.

4. How is trigonometry used in real life?

Trigonometry is used in many real-life applications, such as architecture, engineering, navigation, and astronomy. It is also used in fields such as music and art, as well as in computer graphics and animation.

5. What are some common mistakes when solving trigonometric equations?

Some common mistakes when solving trigonometric equations include forgetting to convert angles to the correct unit, using the wrong inverse trigonometric function, and making sign errors. It is also important to check for extraneous solutions, which can occur when taking the inverse of a trigonometric function.

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