The answer is suppose to be

and im not gettin it can anyone help me?

Another question, What is the difference between and

because they give difference answers?

Printable View

- March 15th 2010, 05:22 PMpurplec16Addition and Subtraction Formulas

The answer is suppose to be

and im not gettin it can anyone help me?

Another question, What is the difference between and

because they give difference answers? - March 15th 2010, 05:47 PMsa-ri-ga-ma
(2*sqrt3 + 4)/-2 = 2*sqrt3/-2 + 4/-2 =.........?

And

tanA + tanB is not equal to tan(A+B)

tan(A+B) = (tanA+tanB)/[1-tanA*tanB] - March 15th 2010, 05:51 PMTKHunny
1) "The answer is supposed to be..."

That is what you have. Try some algebra. There is a reason why you studied "simplification" over and over and over.

2) What is the difference.

Simply, you do not understand the concept fo funciton notation.

f(a) is a function operating on a value 'a'.

f(b) is a function operating on a value 'b'.

f(a+b) is a function operating on the value 'a + b'.

f(a) + f(b) is ths sum of a function operating on a value 'a' and that same function operating on a value 'b'.

I am not encouraged that 1) You started the problem with the wrong expression and 2) you only got so far as to wonder "they give different answers". You really should start understanding what you are doing. One day you will discover the mathematics is not just a class to get through. - March 15th 2010, 05:52 PMpurplec16
I know how to do the question, Thanks alot I understand now I was just kind of confused

- March 15th 2010, 06:27 PMpurplec16
I have another question that I really need help with

If and are acute angles such that and

Find:

and

Which quadrant contains ? - March 15th 2010, 06:29 PMArchie Meade
hi purplec16,

x(60)+x(225)=x(60+225)

That's algebraic multiplication.

Tan(angle) is a "trigonometric function".

So you must study the difference. - March 15th 2010, 06:43 PMArchie Meade
You will need to work these out using Pythagoras' Theorem

and also the following trigonometric identities

To start, draw 2 right-angled triangles.

For the first

Therefore

So there is something wrong here as the opposite cannot be longer than the hypotenuse

since the hypotenuse is the longest side of a right-angled triangle.

Then, when you use Pythagoras' theorem, you find the 3rd side

and you can write

Do the same with the 2nd triangle, using

Again you get the 3rd side of that to help you write and - March 15th 2010, 06:58 PMpurplec16
sorry it is [tex]cos\alpha[\math], I see why cos has to do with it, but I dont see how tan comes into play?

- March 15th 2010, 07:03 PMArchie Meade
ok,

just use

Adjacent=4, hypotenuse=5.

Draw the triangle.

Pythagoras' theorem gives

Use this to find the length of the 3rd side.

Then write

Finally use the trigonometric identity.

You need and also.

You get these when you have the 3rd side of the 2nd triangle.

gives you 2 of the 3 sides of that one.

Pythagoras theorem gets you the 3rd.

Then you can write and

before using the trigonometric identity. - March 15th 2010, 11:14 PMGrandad
- March 16th 2010, 04:29 PMpurplec16
- March 16th 2010, 05:29 PMArchie Meade
It isn't a matter of figuring out which quadrant the angle is in, purplec.

The question does not ask you to find the angle.

It's asking for and

Are you able to use Pythagoras theorem to write

? - March 16th 2010, 05:31 PMpurplec16
Yes I am i got the question but it ask the quadrant of alpha + beta?

- March 16th 2010, 05:39 PMArchie Meade
Ok,

well, once you have found out what

and are

you find out the quadrant of the angle using the following...

gives the vertical co-ordinate of a point on the unit circle circumference, centred at (0,0).

gives the horizontal co-ordinate.

Hence,

sin + and cos + is the 1st quadrant 0-90 degrees

sin + and cos - is the 2nd quadrant 90-180 degrees

sin - and cos - is the 3rd quadrant 180-270 degrees

sin - and cos + is the 4th quadrant 270-360 degrees