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Can someone please help me with this question? Prove the identity (2cos0.5X - 1 - cosX)/(2cos0.5X + 1 + cosX) = (1 - cos0.5X)/(1 + cos0.5X) (farrrrrrr....it's 12:40 on a Sunday night during school holidays.....and I'm doing maths.)

54. Use compound angle formula for tan on the LHS. 55. Use double angle formula for tan on the LHS where possible and cancel things out. 43. Use the double angle formula for cos twice, then expand the square. 40. Use compound angle formula for tan. Combine the two fractions. Expand and simplify...

Sure, go ahead. For proving identities, you just need to do a wide range of questions so you don't get stuck with something you've never seen before during the exam.

Look for things that can cancel out. If the question was simplify 1 + cos2x then you would use the formula cos2x = 2cos^2(x) - 1 because + 1 and -1 would cancel out. i.e. 1 + cos2x = 1 + [2cos^2(x) - 1] = 2cos^2(x) Another situation would be: if everything else was in terms of sin...

Yeah they gave me the formula and asked me to prove it. I proved like half of it and then just wrote = RHS But for some reason, the marker gave me full marks for it even though I didn't fully prove it. (Probably lazy marker LOL) I didn't get any marks for the next part though.

Yeah on products. They asked to derive the formula first and then solve it. I came top 10 for my 4u assessment but only average for my 3u assessment. An absolute disaster indeed. My teacher teaches very fast in class and sometimes I don't end up doing all the homework. i.e. what I learn in...

Thanks guys. Yeah my school has taught it. There was also a question on it in my 3u first assessment, and I couldn't do it in the exam :( It seems like I forget everything very quickly if I don't touch it for a while. Not enough practice I guess... I'm currently doing chapter 21 in the...

I'm having difficulties doing products as sums or differences questions. I can eventually do them, but each question takes ages to do because it takes a long time to derive the formulas from the double angle formulas in my head. So for all you people good at trig, what's the best way to...