Dear all,

Could you kindly help me with these 2 sums - Q 18 and Q21 - many, many thanks :)

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- Feb 12th 2010, 06:37 PMDrdjTrigo Sums
Dear all,

Could you kindly help me with these 2 sums - Q 18 and Q21 - many, many thanks :) - Feb 14th 2010, 10:50 AMGrandad
Hello DrdjI think one of the reasons no-one has attempted to answer question 18 is that the diagram is not clear. We can't see the graph of at all. This means that it's not possible to be sure what the value of is. However, here is some working and a diagram showing two possible solutions. You will have to take it from here.

First crosses the -axis where:

So let's suppose first that this graph meets where . Then:

But perhaps the diagram shows a different position of the graph, and they actually meet at a different point at which the first graph crosses the -axis; for instance, where . Then we get:

Over to you. Can you sort it out now?

For question 21: multiply top-and-bottom by :, if we are given that is acute, because is then positive.

Grandad - Feb 14th 2010, 05:44 PMDrdjThanks
Dear Grandad,

You're simply wonderful !!

Apologies for the not-so-clear scan of Qn 18 - causing the confusion ....

But thank you so much for your detailed and clear explanation, not to mention to the colorful graphs plotted !! :))