Further Maths AQA GCSE Help Watch

Youssef Dahi
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Question 4i is getting on my nerves. I’ve just started this topic, so it’s new to me.
I can use the other identity confidently. But I have no idea how to use this identity
I tried watching videos but I still can’t seem to get the answer.
Can someone explain it to me as if you’re talking to a Year 7 student?
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begbie68
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Hopefully you already to understand how to solve the following 3 types of trig equations, for example for 0<x<=360 :

1. b.cos(ax+c) = d
2. b.sin(ax+c) = d
&
3. b.tan(ax+c) = d

So, you cannot directly solve an equation which has a mixture of trig functions.
eg a.sin^2(x) + b.cos(x) + c = 0
without using an identity to replace in this case sin^2(x) by (1-cos^2(x)) and then you have an equation (quadratic in this case) in just one type of trig function
this example after rearranging and solving would give
cos(x) = A , or cos(x) = B
and you say you can already use this identity, so I expect you've already seen (and solved) a number of eqns like this ??

Then, there are three (or more) equations of the type you've given here where we use tan(x) = sin(x) / cos(x) identity to rearrange a given equation we cannot solve directly into another equation which we CAN solve.

ii) and iii) demonstrate an issue of making sure that we factorise effectively.

One of these questions will become
cos(x).[4sin(x) - 1] = 0
so either cos(x) = 0 , or 4sin(x) - 1 = 0

and you should be able to finish & solve it from here ....

hth

Let me know if you've any further questions
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