Proving trignometric identities.

  • Thread starter Matriculator
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In summary, the user is struggling with two problems in a chapter they understand better than previous ones. They are looking for guidance and have received suggestions to rewrite the equations in terms of sine and cosine before simplifying. They are also advised to work on the left side first before attempting to manipulate the right side.
  • #1
Matriculator
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Homework Statement


I understand this chapter a little better than the previous ones, but I'm having problems with these two problems. Can anyone at least lead me in?


Homework Equations





The Attempt at a Solution


Starting from the right side for both. For the second one, turning the 1 into cos2α+sin2α. cot2α+cos2α+sin2α? I'm not sure of if this a good start, because I'm stuck from this point on.
 

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  • #2
I personally find the use of tan, cot and csc quite confusing. I always prefer to just rewrite everything in terms of sin and cos and then the simplification sometimes becomes more obvious.
 
  • #3
Matriculator,

As CompuChip suggested, rewrite the [itex]\tan[/itex] and [itex]\cot[/itex] as fractions of [itex]\sin[/itex] and [itex]\cos[/itex]. Then, make sure you have common denominators before adding or substracting.

J.
 
  • #4
Matriculator said:

Homework Statement


I understand this chapter a little better than the previous ones, but I'm having problems with these two problems. Can anyone at least lead me in?

Homework Equations



The Attempt at a Solution


Starting from the right side for both. For the second one, turning the 1 into cos2α+sin2α. cot2α+cos2α+sin2α? I'm not sure of if this a good start, because I'm stuck from this point on.
attachment.php?attachmentid=56945&d=1363858981.png


Why do you want to work on the right side on either of these?

Work on the left side using the excellent suggestions of the previous responders. It's fairly straight forward to get the left hand side to agree with the right hand side.

... then if you must work only on the right hand side, reverse the steps you used on the left side.
 

1. How do you prove a trigonometric identity?

To prove a trigonometric identity, you must use algebraic manipulation and trigonometric identities to show that both sides of the equation are equal.

2. What is the purpose of proving trigonometric identities?

The purpose of proving trigonometric identities is to show the relationship between different trigonometric functions and to verify that they are mathematically equivalent. This can also help in solving complex trigonometric equations and simplifying expressions.

3. What are some common strategies used to prove trigonometric identities?

Some common strategies used to prove trigonometric identities include using the Pythagorean identities, factoring and simplifying expressions, substituting values for variables, and converting all trigonometric functions into sine and cosine functions.

4. Are there any tips for successfully proving trigonometric identities?

Yes, some tips for successfully proving trigonometric identities include starting from the more complex side of the equation, using known identities and formulas, and being familiar with the properties of trigonometric functions such as their domains and ranges.

5. What are some common mistakes to avoid when proving trigonometric identities?

Some common mistakes to avoid when proving trigonometric identities include forgetting to consider the restrictions on the domains of trigonometric functions, making incorrect algebraic manipulations, and not using the correct identities or formulas.

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