Why do I get a parser/syntax error on a variable name in openSCAD?

Question

I am new to openSCAD and I am trying to recreate a piston animation based on a youtube video I saw by a channel called "mathcodeprint". My code is almost identical, except I had to create the modules myself because he never shows them in the video.

I am getting a parser/syntax error in my code on line 6 where the variable "pin_offset" is defined. However, and if I try to hardcode and remove the variables entirely I get a similar issue on line 9 where "THROW" begins. Can someone please help me determine what the issue is? The code is here:

$fn=200;
//$t=0

crank_rad = 30;
crank_ang = $t*360
pin_offset = 55;
rod_length = 80;

THROW = sqrt((pow(crank_rad,2)+pow(rod_length,2))-(2*crank_rad*rod_length*cos(crank_angle)));

rod_ang = asin(crank_rad*sin(crank_ang)/rod_length);

translate([75,0,0]) text(str(THROW));
translate([75,-20,0]) text(str(rod_ang));


translate([0,0,THROW-rod_length]) piston()

%translate([0,0,THROW-rod_length]) pin()

#translate([0,-5,pin_offset+THROW-rod_length]) rotate([0,-rod_ang,0]) conrod()

translate([0,0,rod_length+pin_offset]) rotate([0,crank_ang,0]) cam();



module piston(){
    difference(){
        cylinder(h=75,r=50,center=false);
        translate([0,0,pin_offset]) rotate([0,90,0]) cylinder(h=60,r=5,center=true);
    }
    translate([0,0,-5]) cylinder(h=80,r=55,center=false);
}

module pin(){
    translate([0,0,pin_offset]) rotate([0,90,0]) cylinder(h=60,r=5,center=true);
}

module conrod(){
    hull(){
    difference(){
        translate([0,-5,pin_offset]) rotate([0,90,0]) cylinder(h=5,r=5,center=false);
        translate([0,-5,pin_offset+rod_length]) rotate([0,90,0]) cylinder(h=5,r=5,center=false);
    }
    translate([0,-5,pin_offset]) rotate([0,90,0]) cylinder(h=5,r=7,center=false);
        translate([0,-5,pin_offset+rod_length]) rotate([0,90,0]) cylinder(h=5,r=7,center=false);
}
}
    
module cam(){
translate([0,-5,pin_offset+rod_length]) rotate([0,90,0]) cylinder(h=10,r=5,center=false);
}

Answer 1

the semicolon is missing in the line before

crank_ang = $t*360; 

and line 9 has to be

THROW = sqrt((pow(crank_rad,2)+pow(rod_length,2))-(2*crank_rad*rod_length*cos(crank_ang)));