All Answers 352760 Answers

Let total number of fish be T.  Then    0.3*T = 18  so T = 18/0.3  or T = 60

Hi Melody

For Example:

\(\begin{array}{|lrclrcl|} \hline (1) & \sin(x+y) &=& \sin(x)\cos(y) +\cos(x)\sin(y) \\ (2) & \sin(x-y) &=& \sin(x)\cos(y) -\cos(x)\sin(y) \\ \\ \hline \\ (1)-(2): & \sin(x+y)-\sin(x-y) &=& \sin(x)\cos(y) +\cos(x)\sin(y) \\ &&&-\Big(\sin(x)\cos(y) -\cos(x)\sin(y)\Big) \\ & \sin(x+y)-\sin(x-y) &=& \sin(x)\cos(y) +\cos(x)\sin(y) \\ &&& -\sin(x)\cos(y) +\cos(x)\sin(y) \\ & \sin(x+y)-\sin(x-y) &=& \cos(x)\sin(y) +\cos(x)\sin(y) \\ & \sin(x+y)-\sin(x-y) &=& 2\cos(x)\sin(y) \\ \\ \hline \\ (3): \mathbf{x+y = A} \\ (4): \mathbf{x-y = B} \\ \\ (3)+(4): & 2x = A+B \\ & \mathbf{x = \dfrac{A+B}{2}} \\\\ (3)-(4): & 2y = A-B \\ & \mathbf{ y = \dfrac{A-B}{2}} \\\\ \hline & \sin(x+y)-\sin(x-y) &=& 2\cos(x)\sin(y) \\ & \sin(A)-\sin(B) &=& 2\cos\left(\dfrac{A+B}{2}\right)\sin\left(\dfrac{A-B}{2} \right) \\ \hline \end{array}\)

PartialMathematician,

Yes, I believe you do have to sign up to share graphs with others. It is free.

atan(-8413.3) = -89.993189856627 degrees

.993189856627*60 = 59.59139139762

0.59139139762*60 = 35.4834838572

so

\(atan(-8413.3)=-89^\circ\;59'\;35.43''\)

Perhaps 186,7-172/0,4*20  needs to have brackets added?

Возможно, 186, 7-172/0,4 * 20 необходимо иметь скобки добавил?

I do not know where your 94 degrees comes from.

Я не знаю, где ваши 94 градусов приходит от.

Thanks very much Heureka,

Those formulae  2 and 3 that you have used, do you have those memorised?

I mean can they be derived easily enough? 

I do not remember seeing them before....

​ Trigonometric Identities - 2

\(\text{Formula } 1: \boxed{\sin(A+B) = \dfrac{2\cdot \tan \left(\frac{A+B}{2} \right)} {1+\tan^2\left(\frac{A+B}{2} \right) } }\\ \text{Formula } 2: \boxed{\cos(A)-\cos(B) = -2\sin\left(\frac{A+B}{2} \right)\sin\left(\frac{A-B}{2} \right) } \\ \text{Formula } 3: \boxed{\sin(A)-\sin(B) = 2\cos\left(\frac{A+B}{2}\right)\sin \left(\frac{A-B}{2} \right) } \)

\(\begin{array}{|rcll|} \hline \dfrac{p}{q} &=& \dfrac{\cos(A)-\cos(B) } {\sin(A)-\sin(B) } \\\\ &=& \dfrac{-2\sin\left(\frac{A+B}{2} \right)\sin\left(\frac{A-B}{2} \right) } { 2\cos\left(\frac{A+B}{2}\right)\sin \left(\frac{A-B}{2} \right) } \\\\ &=& - \tan \left(\frac{A+B}{2} \right) \\ \mathbf{\tan \left(\frac{A+B}{2} \right)} &\mathbf{=}& \mathbf{- \dfrac{p}{q}} \\ \hline \end{array}\)

\(\begin{array}{|rcll|} \hline \sin(A+B) &=& \dfrac{2\cdot \tan \left(\frac{A+B}{2} \right)} {1+\tan^2\left(\frac{A+B}{2} \right) } \\\\ &=& \dfrac{2\cdot \left( \dfrac{-p}{q} \right) } {1+\left( \dfrac{-p}{q} \right)^2 } \\\\ &=& -\dfrac{2\cdot p } {q\left(1+ \dfrac{p^2}{q^2} \right) } \\\\ &=& -\dfrac{2\cdot p } { q+ \dfrac{p^2}{q } } \\\\ \mathbf{\sin(A+B)} &\mathbf{=}& \mathbf{-\dfrac{2pq } { p^2+q^2 } } \\ \hline \end{array}\)

Градус, минута, и секунда

да. и потом arctg перевести не могу. и ответь должен примерно вот такие цифры 94°12'30"

Hello! I can not arct find. how to count arct 186.7-172 / 0.4 * 20 =

it fights (degrees, minutes, seconds), for example 94 ° 12'30 "

Mmm not sure what you are asking.

Ммм не уверена, что ты просишь.

186.7-172 / 0.4 * 20 = = -8413.3

You don't need to ask this question...

because you can use the calculator (\(\frac{8}{9}\)) ...

and also get the answer of (0.8888888888888889) as the "final answer"...

the two are identical

I also offer a calculator aid to help although this may not be what you need.

Look in thew sticky topics on the left and open the post called 'reference material'

Now scroll down to the heading "Other Calculators"

There is one there called "z score probabilities - this is great"

Try that and you should be able to answer your questions I think.

There are many great things in the sticky topic posts, especially in 'reference material' one.

I do not think either of those sites would be helpful in answering this question PM!

In LaTex, it would be​ \(y = 1, 200\cdot 1.02^x\)

I do not think that you have included the whole question.....

If you want to use "-->" or "==>" in LaTeX, it is $\Rightarrow$. 

I think Vieta's formula might work in here, but I am not sure how to proceed.

I am pretty sure this is number theory. 

Do you have to sign up in Desmos to share a graph link? I tried to share one, but even when I plotted points on the graph, the URL was still https://www.desmos.com/calculator. (The link brought me to a empty graph)

If you want to use "-->" or "==>" in LaTex, it is $\Rightarrow$. 

https://www.usatoday.com/story/money/business/2014/09/06/wscs-cash-a-thing-of-the-past/15075047/

https://www.desmos.com/calculator

\(\dfrac 4 9 + \dfrac 1 6 + \dfrac{5}{18} = \\ \dfrac{8}{18}+\dfrac{3}{18}+\dfrac{5}{18} = \\ \dfrac{8+3+5}{18} = \\ \dfrac{16}{18} = \\ \dfrac 8 9\)

Second one

-135°   =  360 - 135   =  225°

So...we have   (3, 225°)

This one is easy.....it is a 45° angle in the 3rd Quadrant  

The sine and cosine are equal here....so the x,y coordinates will be the same

cos 225  =  x / 3

3cos 225  = x

3 ( -1 /√2)  = x

-3/√2  = x   = y

So

(x , y )   =  ( -3/√2 , -3/√2 )