Trigonometric Identities for Sine and Cosine

In summary, the equation 4*sin(theta)=3*csc(theta) can be simplified to sin(theta)=sqrt(3)/2. The possible values for theta are 30 degrees, 60 degrees, 150 degrees, and 330 degrees. It is important to differentiate between sine and cosine in order to avoid confusion.
  • #1
abstrakt!
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Homework Statement



[itex]4 \ sin \ \theta \ = \ 3 \ csc\ \theta[/itex]

The Attempt at a Solution



[itex]sin\ \theta \ = \ \frac {3}{4} \ csc \ \theta[/itex]

[itex]sin^2 \ \theta \ = \ \frac {3}{4} [/itex]

[itex]sin \ \theta \ = \ \pm \ \frac {\sqrt{3}}{2}[/itex]

[itex]30 \ \deg \ in \ QI, \ 150 \ \deg \ in \ QII, \ 210 \ \deg \ in \ QIII, \ 330 \ \deg \ in \ QIV[/itex]

Am I doing this correctly?
 
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  • #2
Almost, but I think you have confused sine and cosine
sin(30 degrees)=1/2
sin(60 degrees)=sqrt(3)/2
cos(30 degrees)=sqrt(3)/2
cos(60 degrees)=1/2
 
  • #3
lurflurf said:
Almost, but I think you have confused sine and cosine
sin(30 degrees)=1/2
sin(60 degrees)=sqrt(3)/2
cos(30 degrees)=sqrt(3)/2
cos(60 degrees)=1/2

I understand the difference between the two, I must have hit the wrong button in my calculator. Thanks brotha.
 

FAQ: Trigonometric Identities for Sine and Cosine

1. What is the difference between sine and cosine?

Sine and cosine are both trigonometric functions used to calculate the relationship between the sides and angles of a right triangle. The main difference between them is that sine represents the ratio between the length of the opposite side and the length of the hypotenuse, while cosine represents the ratio between the length of the adjacent side and the length of the hypotenuse.

2. How do you find the sine and cosine of an angle?

To find the sine and cosine of an angle, you can use a scientific calculator or a trigonometric table. Alternatively, you can use the following formulas: sine = opposite/hypotenuse and cosine = adjacent/hypotenuse. Simply plug in the corresponding values for each side to calculate the sine and cosine of the angle.

3. What are the key properties of sine and cosine functions?

The key properties of sine and cosine functions include periodicity, where the functions repeat themselves after a certain interval, symmetry, where the functions are symmetric about the origin, and amplitude, which represents the height of the curve above or below the x-axis.

4. How are sine and cosine used in real-world applications?

Sine and cosine have numerous real-world applications, including in navigation, engineering, and physics. For example, they can be used to calculate the height of a building or the distance between two points, or to design bridges and buildings that can withstand forces such as wind and earthquakes.

5. How can I improve my understanding of sine and cosine?

To improve your understanding of sine and cosine, you can practice solving problems and working with different values for the sides and angles of right triangles. You can also refer to online resources, such as tutorials and interactive simulations, or seek help from a math tutor or teacher.

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