Answer:
Because u·v=0 they are orthogonal
Step-by-step explanation:
Let's find the solution by using the dot product, taking into account that two vectors are orthogonal if its dot product is equal to 0, so:
u=(cos(o),-sin(o))
v=(sin(o),cos(o))
Let's find the dot product:
u·v=(cos(o),-sin(o))*(sin(o),cos(o))
u·v=cos(o)*sin(o)+(-sin(o)*cos(o))
u·v=cos(o)*sin(o)-sin(o)*cos(o)
u·v=0
In conclusion, for any value of o, u·v=0. So u and v are orthogonal.