acos.s fix: use the formula acos(x) = atan2(sqrt(1-x),sqrt(1+x))

[musl] / src / math / i386 / fmodl.s

.global fmodl
.type fmodl,@function
fmodl:
        fldt 16(%esp)
        fldt 4(%esp)
1:      fprem
        fstsw %ax
        sahf
        jp 1b
        fstp %st(1)
        ret