How do you find the exact value of the third side given triangle RSTRST, RS=9, ST=9sqrt3ST=93, mangleS=(5pi)/6mS=5π6?

1 Answer
Jan 15, 2017

=9sqrt(7)=97

Explanation:

You would apply the cosine theorem to calculate the third side:

bar(RT)=sqrt(bar(RS)^2+bar(ST)^2-2*bar(RS)*bar(ST)*cos hatS)¯¯¯¯¯¯RT=¯¯¯¯¯RS2+¯¯¯¯¯ST22¯¯¯¯¯RS¯¯¯¯¯STcosˆS

=sqrt(9^2+(9sqrt(3))^2-2*9*9sqrt3*cos(5/6pi))=92+(93)22993cos(56π)

=sqrt(81+243-cancel162^81sqrt(3)*(-sqrt(3)/cancel2)

=sqrt(324+243)=sqrt(567)=9sqrt(7)