You don''t need to memorize them.Just solve many numericals using those formulaes.With the application of those formulaes you will remember them.If that doesn''t work make abbreviations and sentences and write every single formula in a seperate copy according to their topics.E.g. in trigonometry learn "Some People Have Curly Brown Hair Tightly Pulled Back".Sin=Perpendicular/Hypotenuse;the first letters.Also sin=1/cosec,cos=1/sec,tan=1/cot

once read all the formulae and then close the book and write them after that practice some questions based on those formulae then u can remember them easily