सदस्य: Melody

mariawave:
the polaroid ultrasonic rangefinder on a camera sends out a pulse with period 5x10^-7s and wavelengh of 1.5x10^-4m the sound bounces off a unicorn and returns to the camera 0.6s later

Hi Mariawave
Before I forget could I please ask you to give your posts more specific names, it is better for everyone. The right people see your post quicker. You will probably get an answer more quickly and when people search the site for info they find relevant topics more easily.

Now for your question.
You have the period which is seconds/wavelength and you have
Wavelength which is metres/wavelengh.
Now metres/wavelength x wavelengh/second= metres/ second
metres/wavelength ÷ seconds/wavelength = metres/ second

(1.5 x 10^-4) /(5 x 10^-7) m/s
= 0.5 x 10^3 m/s
=5 x 10 ² m/s
=500 metres/sec

500 m/s x 0.6 s
=3000 m
The unicorn is 1.5 km away.

I am writing this on a little phone.
If there's any crazy errors, that is why.

I have now done some corrections

Melody10 Feb 2014

+118692

Guest:
9/25

*
Now guest.
did you really help Polytail to understand or were you just showing off?
I'm not criticizing, I like showing off too but why don't you show people how to actually get the answer.
Maybe like this.

36%
Percent means divide by 100 (that's why % has got a 2 little zeros and a sideways divide sign)
so it is
36/100

4 goes into both of those

36/4 over 100/4
= 9 / 25

Melody10 Feb 2014

+118692

John Lothrop:
]Is 1 divided by 19 a repeating decimal?

Yes, it has 18 digits repeating.

140210 1over19.JPG

Melody10 Feb 2014

+118692

Guest:
how do you find the points where two graphs intersect?

You can either find them graphically by drawing the graphs and seeing where they cross.
or
you can do it algebraically by solving the 2 equations simultaneously.

Melody10 Feb 2014

+118692

aahayajn:
exp(-2.42222)/(1+exp(-2.42222) )

Do you mean e ^(-2.42222)/(1+e ^(-2.42222) ) ?

To bring up e ^x you will need to press 'shift' or '2nd' first.
the e ^x has got the power built in. You do not need to press ^ or x ^y. If you do you will probably get an error message.

On you calc you press

shift e ^x - 2.42222 ÷ (1 + ( shift e ^x -2.42222 ) =

Ans 0.081493928

Melody10 Feb 2014

+118692

larakas0745:
what is inverse sine=1.1746?

On your calc press

2nd or shift
sin
1.1746
=

And behold, your answer will appear. Just like magic.

Melody10 Feb 2014

+118692

Keepitculp:
What is sin A = 0.85

You have the sin ratio, you need the angle so you can make A the subject by saying

A = Sin ^-10.85 (A is the inverse sin of 0.85)
or A = asin 0.85 (A is the arc sin of 0.85)
Arc sin and inverse are exactly the same thing.

To get this answer first make sure that your calculator is is set to degrees. There will probably be a little D at the top of the display area.
then press
2nd sin 0.85 =

Melody10 Feb 2014

+118692

Josh:
Log(3x)+4log(5y)-3log(4z) into single log please.

Here are the log identities - you try to work it out yourself. Post again after you have given it your best shot.

http://en.wikipedia.org/wiki/List_of_logarithmic_identities

http://www.mathsisfun.com/algebra/exponents-logarithms.html

Melody9 Feb 2014

यूजर का नाम	Melody
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