Simplify with Trigonometric Identities

In summary, the conversation is about simplifying trigonometric expressions in a physics problem involving a rod with two masses spinning on a circle. The person asks for help on which identities to use and the reply suggests applying the identity sin2 x + cos2 x = 1. The person also asks for direction on how to first apply the identity and the reply suggests factoring out cos2 θ as a common factor.
  • #1
KleZMeR
127
1

Homework Statement




I'm trying to simplify some trigonometric expressions, I'm attaching my work here. This comes from a famous physics problem i.e. the rod with two masses spinning on a circle. I've tried many times but I just can't get it. Any help on which identities to use would really help me.



Homework Equations



I'm attaching the simplified version, the 'answer'


The Attempt at a Solution



I'm attaching my work.
 

Attachments

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  • #2
Apply a couple of times sin2 x + cos2 x = 1
and your last line simplifies to the given answer
 
  • #3
NascentOxygen said:
Apply a couple of times sin2 x + cos2 x = 1
and your last line simplifies to the given answer

Yes, I looked at that identity, but there are 2 different angles in this problem, and also one of my last two terms is dø2*sin2Θ

Any direction on how to first apply the identity would also help?
 
  • #4
Take cos2 θ outside some brackets because it's a common factor.

And you'll see again, there's another common factor in two other terms to treat similarly.
 

What is the purpose of simplifying with trigonometric identities?

The purpose of simplifying with trigonometric identities is to make complicated trigonometric expressions easier to work with and to solve. By using identities, we can reduce the number of terms and factors in an expression, making it more manageable and easier to manipulate.

What are the basic trigonometric identities?

The basic trigonometric identities are sine, cosine, and tangent. These identities define the relationships between the sides and angles of a right triangle. They are represented by the ratios of the sides, such as sine (opposite/hypotenuse), cosine (adjacent/hypotenuse), and tangent (opposite/adjacent).

How do you simplify trigonometric expressions using identities?

To simplify trigonometric expressions using identities, we use algebraic techniques to manipulate the expression and replace it with an equivalent expression. This can involve using the basic trigonometric identities, such as the Pythagorean identity (sin^2x + cos^2x = 1) or the double angle identities (sin2x = 2sinxcosx), to simplify and reduce the expression.

What are the most commonly used trigonometric identities?

Some of the most commonly used trigonometric identities include the Pythagorean identities, the reciprocal identities (cscx = 1/sinx, secx = 1/cosx, cotx = 1/tanx), and the double angle identities. These identities can be used to simplify most trigonometric expressions and are a fundamental part of working with trigonometric functions.

Why is it important to know and use trigonometric identities?

Knowing and using trigonometric identities is important because it allows us to simplify complex expressions and equations involving trigonometric functions. This makes it easier to solve problems in fields such as physics, engineering, and mathematics, where trigonometric functions are commonly used. Additionally, understanding identities helps us to better understand the relationships between different trigonometric functions and how they can be manipulated to our advantage.

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