Single Trigonometric Functions ( trig identities)

In summary, there are several basic trigonometric identities, such as the Pythagorean identity, reciprocal identities, quotient identities, and even-odd identities. These identities can be used to simplify trigonometric expressions and solve equations. Reciprocal identities involve the inverse of a trigonometric function, while quotient identities involve dividing one function by another. Identities can also be used to solve trigonometric equations by manipulating and simplifying them. To remember all the identities, one can use techniques such as flashcards, practice, and understanding the logic behind them.
  • #1
imxaxpunk
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Homework Statement



Cos^2x-Sin^2x/2 SinxCosx



The Attempt at a Solution



I changed cos^2x to 1- sin^2x

which then the equation was 1- s sin^2x/2snxcosx and i have no idea how to make this a single trig. function
 
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  • #2
If you can't see it immediately then, what is 1-2sin2x the same as? What is 2sinxcosx the same as?

Hint: Look up your double angle formulas.
 
  • #3
**Hint**

[tex]sin(a+b)=sina \cdot cosb+sinb \cdot cosa[/tex]

What if a and b where the same number...
 

FAQ: Single Trigonometric Functions ( trig identities)

1. What are the basic trigonometric identities?

There are several basic trigonometric identities, including the Pythagorean identity, reciprocal identities, quotient identities, and even-odd identities. The Pythagorean identity states that sin^2(x) + cos^2(x) = 1, while the reciprocal identities state that sin(x) = 1/csc(x), cos(x) = 1/sec(x), and tan(x) = 1/cot(x). The quotient identities state that tan(x) = sin(x)/cos(x) and cot(x) = cos(x)/sin(x). Finally, the even-odd identities state that sin(-x) = -sin(x), cos(-x) = cos(x), and tan(-x) = -tan(x).

2. How do I simplify trigonometric expressions using identities?

To simplify a trigonometric expression using identities, you can use the basic identities mentioned in the previous question, as well as additional ones such as sum and difference identities, double angle identities, and half angle identities. It is important to know and understand these identities in order to simplify and solve equations involving trigonometric functions.

3. What is the difference between a reciprocal and a quotient identity?

A reciprocal identity involves the reciprocal of a trigonometric function, meaning the inverse of the function. For example, the reciprocal identity of sin(x) is csc(x), which stands for cosecant. On the other hand, a quotient identity involves dividing one trigonometric function by another. For example, the quotient identity for tan(x) is sin(x)/cos(x). Both types of identities are used to simplify expressions and solve equations.

4. Can I use identities to solve trigonometric equations?

Yes, identities can be very helpful in solving trigonometric equations. By manipulating the equations using identities, you can often simplify them and solve for the unknown variable. It may also be necessary to use identities in order to identify and cancel out extraneous solutions.

5. How can I remember all the trigonometric identities?

There are several techniques you can use to remember all the trigonometric identities. One method is to create flashcards or a cheat sheet with all the identities and their corresponding formulas. Another method is to practice using the identities in various problems and equations. Additionally, it can be helpful to understand the logic behind the identities and how they relate to one another.

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