Object making in AC 9,Page 66.

[Anonymous]

Hi,

In the pics above the author is explaining how to get the curvature to apply to the chair back rest, I will appreciate if someone can explain how he got the expression :- angle= 90degress-ATN((A/2)/B)/B))*2,
What is and where does he get ATN ?
Also why multiply by 2(*) ?

I will appreciate your reply

Thank you

Femi

[Anonymous]

atn (x) is the GDL circular function arctangent which returns
an angle derived from the ratio of the opposite/the adjacent
sides of a right triangle. In the diagram this angle is half the
total included angle so the angle must be multiplied by two.
Peter Devlin