Proving: cosA/(1-tanA) + sinA/(1-cotA) = sinA + cosA

  • Thread starter Miike012
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In summary, the conversation discusses how to prove the equation cosA/(1-tanA) + sinA/(1-cotA) = sinA + cosA. The conversation includes attempts at solving it by manipulating trigonometric identities and the realization that (cos^2-sin^2)=(cos-sin)*(cos+sin). The conversation ends with praise for the student's understanding of algebraic manipulations.
  • #1
Miike012
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Homework Statement


Prove:
cosA/(1-tanA) + sinA/(1-cotA) = sinA + cosA


I have tryed turning tan and cot into sin and cos and everything but I can not prove it... can some one help??
Thank you.


Homework Equations





The Attempt at a Solution

 
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  • #2
Not until you show what you did that didn't work.
 
  • #3
cos/(1-sin/cos)+ sin/(1-cos/sin)
cos^2/(cos-sin) + sin^2/(sin-cos)
(cos^2 - Sin^2)/(cos-sin)
 
  • #4
Miike012 said:
cos/(1-sin/cos)+ sin/(1-cos/sin)
cos^2/(cos-sin) + sin^2/(sin-cos)
(cos^2 - Sin^2)/(cos-sin)

That's good! Now (cos^2-sin^2)=(cos-sin)*(cos+sin), right? Just multiply it out.
 
  • #5
O wow, I don't know why I ddint notice that... I think I have been studying to long ha...
 
  • #6
Miike012 said:
cos/(1-sin/cos)+ sin/(1-cos/sin)
cos^2/(cos-sin) + sin^2/(sin-cos)
(cos^2 - Sin^2)/(cos-sin)

I'm very impressed! It hass been a long time since the precalculus forum has seen any consistently correct algebraic manipulations from a student in just 1 post!
 
  • #7
Thank you... I just started doing them yesterday.
 

1. What is the purpose of proving the equation cosA/(1-tanA) + sinA/(1-cotA) = sinA + cosA?

The purpose of proving this equation is to show that it is true for all values of A. This is important because it allows us to confidently use the equation in other mathematical calculations and proofs.

2. How do you prove the equation cosA/(1-tanA) + sinA/(1-cotA) = sinA + cosA?

To prove this equation, we can use the fundamental trigonometric identities and algebraic manipulations. By substituting 1/tanA for cotA and 1/cotA for tanA, we can simplify the left side of the equation to (cosA + sinA) / (1 - tanA). Then, by using the Pythagorean identity sin^2A + cos^2A = 1, we can further simplify the left side to equal sinA + cosA, which is equal to the right side of the equation.

3. What are the fundamental trigonometric identities used in proving this equation?

The fundamental trigonometric identities used in proving this equation are the Pythagorean identity (sin^2A + cos^2A = 1), the quotient identity (tanA = sinA/cosA), and the reciprocal identities (cotA = 1/tanA and cotA = cosA/sinA).

4. Can you provide a visual representation of this equation?

Yes, the equation cosA/(1-tanA) + sinA/(1-cotA) = sinA + cosA can be represented visually using a unit circle. By drawing a right triangle within the unit circle and labeling the sides with the appropriate trigonometric functions, we can see that both sides of the equation are equal to the length of the hypotenuse (represented by the radius of the unit circle).

5. What is the significance of proving this equation?

The significance of proving this equation is that it strengthens our understanding and knowledge of trigonometric identities and their applications. It also allows us to confidently use this equation in other mathematical calculations and proofs. Additionally, proving this equation can serve as a basis for more complex mathematical concepts and theories.

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