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Calling Maths Gurus

cerbera - 31/10/13 at 12:20 PM

My daughter is going to sit the American SAT examine and is doing a bit of study in preperation for this. We've come across a maths question that has stumped both of us, not that we're maths genii, so I'm hoping someone knows the answer but more importantly can explain why.

Cheers

ed1801 - 31/10/13 at 12:28 PM

This should help, and has the explanation.

http://www.mathopenref.com/chord.html

dave_424 - 31/10/13 at 12:38 PM

quote:
Originally posted by ed1801
This should help, and has the explanation.

http://www.mathopenref.com/chord.html

Isn't it asking for the arc length?

Chord length is 2r*sin(c/2)

r = 5
c = 148 degrees

chord length = 9.61261

Arc length = diameter*pi*(angle/360)

= 10*pi*(148/360)

= 12.91544

dave_424 - 31/10/13 at 12:41 PM

Looking again, can you list the possible answers and the angle, I thought it was 16 degrees but is unclear

Dave

cerbera - 31/10/13 at 12:47 PM

Sorry for the bad picture.

The angle is 36
the posible answers are...
A) PI / 2
B) PI
C) 3PI / 2
D) 3PI
E) 7PI / 2

and yes, it's asking for the arc length.

[Edited on 31/10/13 by cerbera]

cerbera - 31/10/13 at 12:53 PM

The more I look at this the more I think that the possible answers are wrong.

dave_424 - 31/10/13 at 12:53 PM

Angle is 180-36-36 which gives you the angle at O = 108 degrees

Arc length = diameter*pi*(angle/360) = 10*pi*(108/360)

=9.42477....

divide by pi gives you 3

Answer = 3pi

matt_claydon - 31/10/13 at 12:58 PM

Angle ODB = 36 degrees, that makes angle BOD = 180-36-36 = 108 degrees.

360/108 = 3 1/3

a full circumference is d * pi = 10pi

10pi / (3 1/3) = 3pi

Edit: too slow!

[Edited on 31/10/13 by matt_claydon]

cerbera - 31/10/13 at 01:00 PM

Ta very much.
Will be able to sleep tonight now