question on maximisation and minimisation in geometry (2 Viewers)

[waltssillyhat]

please help with part b!! this is part of curve sketching using the derivative

 

[C2H6O]

Find dA/dy using product rule and chain rule, treat r as constant, find the value of y where A is max. sub that value of y into the area formula

 

[C2H6O]

Oh btw you don't need to sketch anything just set dA/dy as equal to 0 to find stationary points and solve algebraically, remembering that r and y are positive numbers

 

[waltssillyhat]

Oh btw you don't need to sketch anything just set dA/dy as equal to 0 to find stationary points and solve algebraically, remembering that r and y are positive numbers

do i have to find the second derivative to test if there is a maximum turning point when dA/dy is equal to 0?

 

[coolcat6778]

cambridge math questions for advanced are defintely pointless

 

[waltssillyhat]

cambridge math questions for advanced are defintely pointless

why??

 

[C2H6O]

do i have to find the second derivative to test if there is a maximum turning point when dA/dy is equal to 0?

You mean in case it’s a minimum turning mount instead of a max? No because it works out that way, and you only get 1 answer. Also you could sub it in and you already know what the correct answer is, so if you get that you’re good.