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It is not just trial and error, as this will eat away time in the exam. if you can't see it straight away then you need to consider some things. for example a common question might be find the integral of...

to find the derivative, we can first make this easier to visualise. Say a second variable, y, is included to make this become y = arcsinx. now if we sin both sides, we get siny = x. we already know the de...

Using the question, first use de Moivre's theorem to say (cos x + i sin x)^5 = cos 5x + isin 5x. Now we can use a binomial expansion on the RHS to say 

cos 5x + isin 5x = cos⁵ x + 5i cos...

Firstly rearrange the differential equation to fit the form dx/dt +P(t)x = Q(t). The integrating factor is then found by using the formula:

u = EXP(INTG(P(t))). We know that P(t) = 2t and so by int...

de Moivre's: (cos(x)+isin(x))ⁿ=cos(nx)+isin(nx) set n=2 (cos(x)+isin(x))²=cos²(x)+2isin(x)cos(x)-sin²(x), which, according to de Moivre's cos²(x)+2is...