I want my students to enter the ordered pair for a polar coordinate using exact radian measures. How to I code it so that the student has to enter the answer as (4, -7pi/4)?

mypair = parseOrderedPair(this.latex)

my_x = numericValue(mypair.x)

my_y = numericValue(mypair.y)

check=my_x=4 and my_y=-\frac{7\pi}{4}

correct: check

I get the following error

Syntax error: Unexpected token “-”