Identities sin, cos, tan etc. stuff

In summary, the expression ((cos x)/(1+sin x))+((1+sin x)/(cos x)) can be simplified to secx + 1/secx after expanding the numerator and simplifying.
  • #1
UltimateSomni
62
0

Homework Statement



((cos x)/(1+sin x))+((1+sin x)/(cos x))

Homework Equations

2012-03-05_12-13-36_59.jpg

The Attempt at a Solution



multiplied the left equation by (cos x)/(cos x) and the right fraction by (1+sin x)/(1+sin x)

get ((cosx)^2 +(1+sinx)^2) / (1+sinx) (cos x)

and I have no idea where to go from here
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
UltimateSomni said:

Homework Statement



((cos x)/(1+sin x))+((1+sin x)/(cos x))
What are you trying to do, simplify the expression above?
UltimateSomni said:

Homework Equations




2012-03-05_12-13-36_59.jpg



The Attempt at a Solution



multiplied the left equation by (cos x)/(cos x) and the right fraction by (1+sin x)/(1+sin x)

get ((cosx)^2 +(1+sinx)^2) / (1+sinx) (cos x)

and I have no idea where to go from here
 
  • #3
Yes, the answer being 2 sec x
 
  • #4
Expand the numerator and simplify.
((cosx)^2 +(1+sinx)^2) / (1+sinx) (cos x)
 
  • #5
(1-sinx^2) +1 + sinx +1 - sin x

(1- sinx^2) +2 / (1+sin x)(cos x)

I don't see how that helps
 
  • #6
Mark44 said:
Expand the numerator and simplify.
((cosx)^2 +(1+sinx)^2) / (1+sinx) (cos x)

UltimateSomni said:
(1-sinx^2) +1 + sinx +1 - sin x
The only thing you did that makes sense is replacing cos2(x) with 1 - sin2(x). I don't get what you did go go from (1 + sin(x))2 to 1 + sin(x) + 1 - sin(x).

Mark44 said:
(1- sinx^2) +2 / (1+sin x)(cos x)

I don't see how that helps
 
  • #7
Then what simplifying is there to do?
 
  • #8
Apparently I wasn't clear. (1 + sin(x))2 ≠ 1 + sin(x) + 1 - sin(x), which seems to be what you're saying.

The "simplifying" that you need to do is to expand (1 + sin(x))2 to something it is actually equal to.
 
  • #9
Okay it equals (1+sinx)(1-sinx)
still not way to get to 2secx
 
  • #10
Because that's wrong, too. (1 + sin(x))2 ≠ (1+sinx)(1-sinx), if that's what you're saying.

How do you expand (1 + x)2? This is a similar kind of problem.
 
  • #11
Okay it equals (1+sinx)(1+sinx)
still no way to get to 2secx
 
  • #12
UltimateSomni said:
Okay it equals (1+sinx)(1+sinx)

Expand the expression: apply distributivity to work out the brackets.
 
  • #13
All right got it
 

1. What are the identities for sin, cos, and tan?

The identities for sine, cosine, and tangent are fundamental relationships that describe the ratios of the sides of a right triangle. These identities are:
- sin^2(x) + cos^2(x) = 1
- tan(x) = sin(x)/cos(x)
- 1 + tan^2(x) = sec^2(x)
- 1 + cot^2(x) = csc^2(x)

2. How are these identities used in trigonometry?

These identities are used to solve for missing sides or angles of a right triangle and to simplify trigonometric expressions. They also serve as the basis for many other trigonometric identities and equations.

3. What is the difference between the reciprocal and quotient identities?

The reciprocal identities, such as csc(x) = 1/sin(x), are formed by taking the reciprocal of the trigonometric function. The quotient identities, such as tan(x) = sin(x)/cos(x), are formed by dividing one trigonometric function by another.

4. How do I remember all the trigonometric identities?

It can be helpful to memorize the acronym "SOH-CAH-TOA" to remember the three basic trigonometric identities: sin(x) = opposite/hypotenuse, cos(x) = adjacent/hypotenuse, and tan(x) = opposite/adjacent. Additionally, practicing and using these identities often can help with memorization.

5. Are there any other important identities in trigonometry?

Yes, there are many other important identities in trigonometry, such as the double angle identities, half angle identities, and sum and difference identities. These can be derived from the basic identities and are used to solve more complex trigonometric equations and problems.

Similar threads

  • Precalculus Mathematics Homework Help
Replies
4
Views
829
  • Precalculus Mathematics Homework Help
Replies
7
Views
288
  • Precalculus Mathematics Homework Help
Replies
4
Views
536
  • Precalculus Mathematics Homework Help
Replies
6
Views
2K
  • Precalculus Mathematics Homework Help
Replies
6
Views
2K
  • Precalculus Mathematics Homework Help
Replies
1
Views
977
  • Precalculus Mathematics Homework Help
Replies
7
Views
1K
  • Precalculus Mathematics Homework Help
Replies
5
Views
2K
  • Precalculus Mathematics Homework Help
Replies
2
Views
1K
  • Precalculus Mathematics Homework Help
Replies
15
Views
2K
Back
Top