It's Math Time Again

Yup it's the same. Good one. If you strike an arc from hole 15 to hole 3 it will cross line AB at point C. You don't need the intersecting line.

"Billy G"
 
Formulas are ok...just thought a complete solution would be informative.

Some basic things to know...
360 degrees in a circle
sines, cosines and tangents are ratios of the lengths of sides in RIGHT (90 degree) triangles
sine = opposite side / hypotenuse
cosine = adjacent side / hypotenuse
tangent = opposite side / adjacent side

Its good practice to check your answer against something real...so I drew it out to scale and measured point 9 to 15 at 3-14/16" (best precision of my scale) = 3.875"...0.051" difference from computed answer....

Now...what is the length of b ?

Math.jpg
 
It's been better than 10 years since I had a trig test, but I was taught an easy to remember 'brain helper' for the above formulas.

The story was about a wise Indian Chief who solved all the tribal math problems. His name was Chief Soh-cah-toa. It's important to remember to spell his name correctly.

S(sine) O(opposite) H(hypotenuse) C(cosine) A(adjacent) H(hypotenuse) T(tangent) O(opposite) A(adjacent) The good Chief helped me out quite a bit.
 
answer to question A is 2R x sine of 1/2 delta for chord length; but I'm a surveyor so I didn't feel right answering...

Bob
 
I was taught a similar saying to remember

Oscar Has A Heap Of Apples
O H A O A = O/H, A/O, O/A
 
You can also do this a different way, with the Pythagorean theorem.......I think :biggrin:

I'll try it.
 
Andre said:
You can also do this a different way, with the Pythagorean theorem.......I think :biggrin:

I'll try it.
Click to expand...

Nevermind, you can not. For the Pythagorean theorem you need to know two lengths of Mr.triangle. Only one length is a given.
Trig it is :panic:
 
The last grade I passed in school was 5th grade. I'm more or less self taught at bout every thing I know. So I have to teach my self like a dumby as it looks and sounds russian to me. The teacher can start talking and it sounds like an old charlie brown cartoon after about 2min. wa,wa,wa,wa,wa. So I will attempt to explain the first problem so others like might understand what happened.

360* in every circle. If you divide 360 by the number of holes (or any feature) you will get the degree between holes.

360/16 = 22.5* between holes.

Now we know we need hole 9 through hole 15. Thats 6 holes. So we need to find the angle of the triangle between the two points. We use the 22.5 between each hole, multiplied by the number of holes between the two points which is 6

22.5x6 = 135*

You need to find the Sine of 135* which using a calculator just type the number and hit the sine button with it in Degree mode.

Sine of 135* = .923879532

Now we have all the info we need to find the cord. Remember, it's the equations for the cord of a circle that we are using. So now just multiply the sine of 135* by the dia of the bolt circle.

.923879532x4.25 = 3.9264

Is that easy or what? I hope that reads as basic as it seemed typing it
 
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