How do you go from 8secxtanx to x=0? O.o I hate the trig part of calc, everything else ezpz

8 * sec(x) * tan (x) = 0

8 * ( 1 / cos (x) ) * ( sin(x) / cos(x) ) = 0

8 * sin(x) / cos²(x) = 0

sin (x) = 0

since a fraction equals zero only when its numerator equals zero

x = 0

since, on the given range ( -pi/4 ; pi/4 ), the only root of sine is zero.