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### Author Topic: using function sin-1 in a brain  (Read 3417 times)

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#### bozidar

• 3
##### using function sin-1 in a brain
« on: June 26, 2014, 08:51:07 AM »
i have an RC servo controlled coolant nozzles that needs to find the angle using the sin-1 (arcsin). I just can't seem to get it to work.

the formula is from this site      http://www.mathsisfun.com/algebra/trig-solving-sas-triangles.html

using example 2. It works up till the last part   sin P / 6.9 = sin(117°) / 8.405...
sin P = ( sin(117°) × 6.9 ) / 8.405...= 0.7313...
P = sin-1(0.7313...) = 47.0° to one decimal place
.
To check my math i did each step in a different brain.

In the tool height DRO put 6.9

I tried putting .7313 in the DRO with a brain with the formula  arcsin(a) and still get .8202

The sin-1 of .7313 should be 47 but i get .8202 Is it a bug or am I doing something wrong?

formula arcsin(((0.891)*a)/(sqrt(a^2+2.6^2-2*a*2.6*(-.4539)) puts out .8202

Is there a better formula to use? The information that i have is 2 sides and one angle of the triangle.

#### ger21

• 6,291
##### Re: using function sin-1 in a brain
« Reply #1 on: June 26, 2014, 10:15:35 AM »
.8202 is the arcsin in radians. You need to convert radians to degrees
.8202 * 180/pi = 47 (46.995)
Gerry

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#### bozidar

• 3
##### Re: using function sin-1 in a brain
« Reply #2 on: June 26, 2014, 11:51:20 AM »
thank you.

set my calculator on rad and get .8202