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# C3 simple Q watch

1. Please can someone explain why the angle is tan(60)? Why did they choose the tangent function? I understand the other steps involved in answering the Q.
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2. Maths q.pdf (143.2 KB, 87 views)
3. (Original post by Whosthat?)
Please can someone explain why the angle is tan(60)? Why did they choose the tangent function? I understand the other steps involved in answering the Q.
Uh, the angle is , not . Presumably the tangent function was the easier one to work with but you could have just as well chosen the sine or cosine.
4. (Original post by Zacken)
Uh, the angle is , not . Presumably the tangent function was the easier one to work with but you could have just as well chosen the sine or cosine.
But there must be a reason why they chose tan(60). How did they know which function is the correct one to use? Because I couldn't use cos(60) or sin(60) and get the correct answer.

I've attached the mark scheme.
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5. Answer.pdf (95.8 KB, 44 views)
6. (Original post by Whosthat?)
But there must be a reason why they chose tan(60). How did they know which function is the correct one to use? Because I couldn't use cos(60) or sin(60) and get the correct answer.

I've attached the mark scheme.
They've used - i.e: they constructed a right angle triangle by bisecting the angle. We want to use the tangent function because that gives us information about the adjacent and opposite - which is all we have and want. The hypotenuse is of no use to us.

We know that but we want this in terms of only so lo-and-behold, we need to find a way of writing as a function of - using the tangent gives us allowing us to write as a multiple of which can then be substituted into the formula for volume to turn it into a formula that involves just .

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