Geometry And Trig Question Help!

[joecantwell]

http://engageeducation.org.au/engagedownloads/Practice%20Exams/2014/Further%20Maths/Exam%201.pdf

-The link to the exam so you can see the question and picture (Question 5 Geo And trig)

Dont understand how to find the height of the water level

[ellahurley]

Someone correct me if I'm wrong but I'm fairly sure it requires you to find the length linking the radius to the width line (making a triangle), and you know the radius is 5cm and half of the width at that particular point is 4cm so you have two sides and need to find the other using pythagoras theorem? a2+b2=c2
And then once you have that value you minus it from 5 and ta daaaa!

I think that's right but my brain is a bit muddled from study so anyone feel free to correct me 

[joecantwell]

Thanks for the Help!