Quick matrices question (maths)

[50/50]

my cousin has asked me to solve this, but i really dont know how to

Find the value(s) of k for which the matrix

M =

1/2 k
-k 1/2

is an orthogonal matrix.


any ideas?

 

[Arcade Fire]

On orthogonal matrix is one for which the transpose is the same as the inverse. Do you know how to invert and transpose that matrix?

Edit: What's with all the maths questions tonight?!

 

[50/50]

On orthogonal matrix is one for which the transpose is the same as the inverse. Do you know how to invert and transpose that matrix?

oh duuuh... thats easy

thanks