I have a question for this. In an exam would it suffice just to put the question into the calculator, rather than go through all the writing (it seems a little too much for maybe a question in the HSC exam max 3 marks).
I saw one like this in the 2004 paper. It was only out of 2 so just the calculator would be fine?
I'm assuming that this particular problem is from question 1 (possibly question 2) of the hsc paper? there is usually a question very early on that is complex and is simply there to test that you do know how to use a calculator. the question by OP involved a lot of bracket work, one mistake and you get the wrong answer.
so yea, plugging it into the calc would be fine and indeed what would be expected from this question
if however the question used the word show instead of find, ie
Show the value of:
cos(2pi/5)cos(3pi/5) - sin(pi/10)sin(9pi/10) - 2sin(3pi/5)cos(pi/10) = -2
then trebla's answer is what you would need to provide (but im thinking that would be a 3u/4u type question so not to worry
)
but find usually means they just want a number or quick answer
