mrunknown 1 Report post Posted November 9, 2017 (edited) What up guys. Just got a question regarding the marking system for externals. Simply, I have answered a trigo question in paper 1 that was asking for me to find "tan (2x)" with "cos (x)" given in fraction form. Well..I used the tan (2x) formula to solve as shown here (the 3rd one) -> After answering the paper, I was checking my answers. Then I suddenly recalled "tan (2x)" formula isn't included in the SL syllabus. The markscheme only showed using " [sin (2x)] / [cos (2x)]" to solve the question, nothing related to the 3rd formula in the shown above. In fact, it was worth 6 points if I'm not mistaken. If ever I use the tan (2x) formula above, will I be able to receive full marks? I have already inquired this to my math teacher, he however doubt to answer as he wasn't sure. Would really appreciate your help. Thanks in advance! Edited November 9, 2017 by mrunknown Share this post Link to post Share on other sites

Nomenclature 202 Report post Posted November 9, 2017 An examiner should give you the points assuming you used the first two formulas and worked out the answer from there, regardless of whether it was in the syllabus or a simpler way was available. If IB didn't intend that, they'd outsource the work to factory workers rather than math teachers who would be able to recognize some basic trig. formulas. 1 Share this post Link to post Share on other sites