This tip has the following history. When the author’s students got the routine calculation of engineering mechanics, they were very surprised as since sine of an angle but not the angle appears in the list of initial data. When it was told the lecturer he has surprised too and supposed that some meaning must be. “The meaning” was found after talk with another lecturer who had developed this routine calculation about thirty years ago – at that time when neither computers nor even calculators existed. It was necessary to calculate sin by input angle that’s why it was decided to lighten the student’s life – sin was angle was given but not the angle itself. Calculators and computers solved the problem of finding sin but the problem of input the initial data turned another side – we have to introduce into calculation not angle but sin of the angle.
The solution of this “problem” is showed in the fig. 98 in point 1: we can change the value of sin of an angle from 0.5 to another value in the center of complex operator – new value of the angle will be written in the variable y. Actually we could write here y := asin(0.5), but described technology is used for more difficult problem in point 2. In principle it would rather well to expand the operator “:=” so that we can write the expression such as sin(y) at the left of it.