i have done Project -> Build Settings -> Linker -> General and adding the letter "m" into Additional Libraries.
i got error rodata will not fit in region rom. rom overflowed by 1104 bytes.
my statement is
read_out1 = (10*sqrt(read_out1*10));
Try to set optimization level for the parts of your project that are tested (no more debugging needed). This will reduce code space.
More to save: set Build setting to "Release" and enable optimization "none" for the files still under test.