sin etc of a 90 degree angle

[sportsstar469]

ok whats up everybody. i finished my math course a few weeks ago but i have been thinking of trig so its fresh in my mind for my class coming up un september. anyways iwas thinking of right angle trig and im a little confused.
lets say you have a right triangle with the left most angle as angle c the top angle as angle a the right most angle as angle b.
the 90 degree angle is angle c. my question is this. how would i find sin,cos,tan of angle c. sin is oposite over hypotenuse. well angle c is oposite OF the hypotenuse. same with cosine and tan, angle c's opposite is the hypotonuse. i wish i could draw you guys a picture but sadly i dont know how to do that on here.
and lets assume all the sides are given side a is 2 side b is 3 side c is 4.
if noone understands my question i can try drawing something on paint.

 

[Denis]

Go here: http://id.mind.net/~zona/mmts/trigonome ... angle.html

A picture = 1000 words which I'm not (and I don't think anybody else is) typing out :shock:

 

[sportsstar469]

Go here: http://id.mind.net/~zona/mmts/trigonome ... angle.html

A picture = 1000 words which I'm not (and I don't think anybody else is) typing out :shock:

thats just telling me how to find the sin etc of angle a which is easy for me. im trying to find out how i find that stuff for the right angle since the hypotenuse is also its opposite. that page says nothing about this.
sorry but i didnt find what i needed from this page. did you understand my question i could try to make it clearers.

 

[Denis]

a / SIN(A) = c / SIN(90) ; SIN(90) = 1 : memorize that!

So a / SIN(A) = c; also b / SIN(B) = c

 

[mmm4444bot]

… iwas thinking of right angle trig …

… how would i find sin,cos,tan of [a right] angle …

… lets assume all the sides are given side a is 2 side b is 3 side c is 4 …

Hello Sports Star:

Right-triangle trigonometry deals with acute angles only (i.e., angles between zero degrees and 90 degrees).

We can't apply the Opposite/Hypotenuse or Adjacent/Hypotenuse ratios to a right angle.

There are different ways of viewing trigonometry that allow us to determine sine and cosine ratios for ANY angle, but these ways are not part of the right-triangle-trigonometry viewpoint.

I think it's important for trig students to memorize the following.

sin(90°) = 1

cos(90°) = 0

Also, the following "trigonometric identity" holds true for any angle A for which tangent is defined.

tan(A) = sin(A)/cos(A)

tan(90°) = 1/0

Clearly, tangent is not defined for a 90° angle.

Also, your example triangle does not exist!

Are you familiar with the Pythagorean Theorem?

Cheers,

~ Mark

 

[pka]

i find that stuff for the right angle since the hypotenuse is also its opposite. that page says nothing about this. i didnt find what i needed from this page. did you understand my question i could try to make it clearers.

This is material that you simply must know or learn.
If $\displaystyle \theta=90^o\text{ or }\frac{\pi}{2}\text{ ,a right angle}$ then
$\displaystyle \begin{array}{rcl} {\sin (\theta )} & = & 1 \\ {\cos (\theta )} & = & 0 \\ {\tan (\theta )} & = & \text{undefined} \\ {\sec (\theta )} & = & \text{undefined} \\ {\csc (\theta )} & = & 1 \\ {\cot (\theta )} & = & 0 \\ \end{array}$

 

[sportsstar469]

a / SIN(A) = c / SIN(90) ; SIN(90) = 1 : memorize that!

So a / SIN(A) = c; also b / SIN(B) = c

i assuming this is for trig other than right triangle? anyway thanks for the help!

 

[sportsstar469]

Re:

… iwas thinking of right angle trig …

… how would i find sin,cos,tan of [a right] angle …

… lets assume all the sides are given side a is 2 side b is 3 side c is 4 …

Hello Sports Star:

Right-triangle trigonometry deals with acute angles only (i.e., angles between zero degrees and 90 degrees).

We can't apply the Opposite/Hypotenuse or Adjacent/Hypotenuse ratios to a right angle.

There are different ways of viewing trigonometry that allow us to determine sine and cosine ratios for ANY angle, but these ways are not part of the right-triangle-trigonometry viewpoint.

I think it's important for trig students to memorize the following.

sin(90°) = 1

cos(90°) = 0

Also, the following "trigonometric identity" holds true for any angle A for which tangent is defined.

tan(A) = sin(A)/cos(A)

tan(90°) = 1/0

Clearly, tangent is not defined for a 90° angle.

Also, your example triangle does not exist!

Are you familiar with the Pythagorean Theorem?

Cheers,

~ Mark

what a great answer!! i knew there had to be some sort of rule i was missing. and ill memorize what you just said 5 stars for a great answer!

 

[mmm4444bot]

a / SIN(A) = c / SIN(90) ; SIN(90) = 1 : memorize that!

So a / SIN(A) = c; also b / SIN(B) = c

i assuming this is for trig other than right triangle? anyway thanks for the help!

Denis and I say, "you're welcome".

The proportionality that Denis used applies to any triangle, not just right-triangles.

It's another example of trigonometric identities.

For any triangle with side lengths a, b, c, and corresponding opposite angles A, B, C, the following proportions are true.

sin(A)/a = sin(B)/b = sin(C)/c

The equality of these three ratios, each to one another, is known as "The Law of Sines".

These are the sorts of things that you'll learn in trigonometry.

As I mentioned before, there are different viewpoints (i.e., approaches to learning the subject).

Right-triangle trigonometry deals with situations where angles are fixed.

When angles are changing over time, we need a different approach. We even need a new system for measuring continuously-changing angles because degrees are too cumbersome to represent smooth growth or shrinkage of angles.

This new system is called Radian measure. Radian measure uses the length of an arc that's subtended by an angle when the angle's vertex is placed at the center of a circle. (Think of a radar screen.)

As an angle grows, it sweeps out an arc length along the circumference of a circle. It turns out that an angle has measure 1 radian when this arc length equals the radius of the circle.

Wow! That's a lot to absorb, all at once, without pictures. :shock:

To summarize, we use right-triangle trigonometry with fixed angles measured in degrees (although, radian measure works here, too).

We use unit-circle trigonometry with changing angles measured in radians.

The trigonometry of fixed angles and the trigonometry of changing angles share a lot in common.

Like I said, these are the sorts of things you'll learn about in trigonometry.

See ya later.

 

[sportsstar469]

yeah i went over law of sines and cosines in my last class and some angle of elevation word problems etc in that class. got an A
but yeah i never learned the radian or unit circle stuff and i am assuming that stuff is pretty tricky. i just know basic right triangle trigonometry, and the special triangles like equilateral and the 45 degree ones.

but when i was thinking to myself about sins, cosines and tans i was just so confused on what the sine of the right angle of a triangle could possibly be since op/hy is=hy/hy which is as you said undefined so i just had to ask. and you cleared it up for me that in right triangle trigonometry you cant find the sin etc of a right angle just the other angles.

idk if you guys would know this but does a general chem course in college involve a lot of math. i know the intermediate algebra course i just took was a prerequisite for it, but my bio 101 class had an algebra prequisite and we only did math the first day(unit conversions) all i can remember about chemistry is balancing equations,finding moles etc and i know chem was a pain in the hiney. bio is easy though.

 

[mmm4444bot]

… does a general chem course in college involve a lot of math …

Hey there, I'm not sure what amount of math you would consider to be a lot, so I'll answer "yes".

It won't be as much math as a math course, but it will definitely be more math than a biology course.

It's been 20 years or so, but I remember the following in chemistry.

Understanding rules of significant figures

Understanding special rounding rules for chemistry

Finding the equations of lines

Plotting data and drawing graphs

Interpreting data and interpreting graphs

Symbolic reasoning and algebraic manipulations

Working with logarithms

Solving systems of equations

Is that a lot?

 

[sportsstar469]

Re:

… does a general chem course in college involve a lot of math …

Hey there, I'm not sure what amount of math you would consider to be a lot, so I'll answer "yes".

It won't be as much math as a math course, but it will definitely be more math than a biology course.

It's been 20 years or so, but I remember the following in chemistry.

Understanding rules of significant figures

Understanding special rounding rules for chemistry

Finding the equations of lines

Plotting data and drawing graphs

Interpreting data and interpreting graphs

Symbolic reasoning and algebraic manipulations

Working with logarithms

Solving systems of equations

Is that a lot?

well im going to be positive and say if i could handle the math and get an A in my last 6 week math course i can easil;y handle it in this 15 week gen ed course! however i kind of screwed myself over. this semester im taking bio 102 which has a lab to it, chem 101 which has a lab to it, and math 152(trig/) . i usually stay after my math classes and ask the teacher a lot of questions to make sure im clear however on wendsdays my math class ends at 145 and my chem lab begins on 2 o clock so i dont know how successful i am going to be! and then at 6 pm i have bio lab!
unfortunately all the chem labs are filled so im stuck in this class!