Am I right??? Math geniuses please!

Pre-College Topics High School Life
1

<p>okay… I just had my Math final today… I want to know if I got this answer correct or not!
here it is:</p>

<p>The normals to the curve 2y=3x^3 -7x^2+4x at points O: (0,0) and A: (1,0), meet at point N</p>

<p>a) find point N</p>

<p>b) Calculate the area of OAN.
(the question was worth 5 marks)</p>

<p>I had this question in my book, but I never REALLY looked through it. I remembered the point N was (4/5,-2/5)… So i just put it in the graph and then for the area:</p>

<p>I used the cosine rule to get the angle: 108.2… then I used the area of triangle sine rule to get an area of 0.15… however, everyone else used the 1/2 base * height method and ended up with 0.2… Am I wrong??? in the answer key, the answer is 0.2 BUT I STILL THINK MY ANSWER IS PRETTY ACCURATE. HELP PLEASE!</p>

<p>how many marks, out of 5, will I get on this???</p>

<p>Thank you.</p>

2

<p>I think your point for N is wrong… I think it’s (2/5,-1/5) Although that may not be accurate because I’m doing the calculus in my head.</p>

3

<p>haha. No, the N is correct. Its in the answer key and everything… So, do you know if the rest of it is correct???</p>

4

<p>No… 0.2 is correct. I don’t know what you did with the cos rule because ONA is a right angle. the two sides are sqrt(0.8) and sqrt(0.2), (which I reached by Pythagoras of the constituents) then if you use Pythagoras on the big triangle it works out to 1 which is the length of the hypotnouse therefore 1/2 * base * height applies and the answer is 0.2.</p>

5

<p>****eee… THERES NO WAY I CAN PICK UP ATLEAST 3/5 OF THIS??</p>

6

<p>^ Sorry but no, your answer was wrong and you got the method wrong…</p>

7

<p>I got N = (1/5, 2/5) and area = 1/5.</p>

8

<p>^that’s what everyone else got… bahhhh… I dont know why I had to be off by 0.05… maybe the teacher’ll round it to 2 significant figures, no?</p>

9

<p>Uh, probably not, because it’s a rational number.</p>