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SIMPLE MATH ERROR CALCULATION

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Jorge Calderon
Jorge Calderon on 13 Jun 2021
Edited: madhan ravi on 13 Jun 2021
I just need to do a simple math operation (9.2 x 9.2), wich result is 84.64. But somehow MATLAB give me a 84.699999999990 result I don't know why, I need the exact result of the operations because this result makes my servomotor go +90°, and wuth 84.64 it goes -90°.
q3b4=9.2^2;
q3b5=9.2*9.2;
Both q3b4 and q3b5 have the same result.

Answers (2)

Sulaymon Eshkabilov
Sulaymon Eshkabilov on 13 Jun 2021
MATLAB's accuracy is not absolute and thus, such offsets will be present. You can select how many decimal digits you need using vpa() if you have Symbolic MATH toolbox.
https://www.mathworks.com/help/symbolic/digits.html#:~:text=By%20default%2C%20MATLAB%C2%AE%20uses,32%20digits%20by%20using%20digits%20.

madhan ravi
madhan ravi on 13 Jun 2021
Edited: madhan ravi on 13 Jun 2021
Click on the tag floating-point
round((9.2^2 * 1e2) / 1e2, 3) % since you're using a hardware , not sure using a sym class would be acceptable for it
ans = 84.6400

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