Maximum volume of a cone made this way?

Taken from the GCHQ sample aptitude test, we want to work out the maximum value of a cone made my cutting out a sector of a circle and gluing the two edges together to form a cone. Want to send me a fun maths problem or theorem, or just want to say hi? Email me: jpimaths@gmail.com Follow me on Instagram: @jpimaths   / jpimaths   Don't forget to subscribe, it's *FREE*:    / @jpimaths   And, as always, any comments, feedback or suggestions are welcomed! Thanks. PS. I'm also available for private tutoring! As someone who has successfully studied maths at Oxford University, I can help you in achieving your dreams of studying maths at a top university. I have over 2 years of experience tutoring maths to prospective Oxbridge students! Email me using the email address above to get more details!