Arccos(x)`=-1/(√(1-x²)
arccos²(x)`=-2*arccos(x)/√(1-x²)
1/arccos²(x)=(1`*arccos²(x)-1*arccos²(x)`)/arccos⁴(x)=
=(0-(-2*arccos(x)/√(1-x²))/arccos⁴(x)=2*arccos(x)/(arccos⁴(x)*√(1-x²)).
Y=5x/2 z=6x/2=3x
Подставляем:
(x^2+25x^2/4+9x^2)/(5x^2/2+15x^2/2+3x^2)= (1+25/4 +9)/(5/2+15/2+3)=(65/4)/13=5/4
Ответ:5/4