1. Let R be the counterclockwise rotation by 90 degrees. Vectors r1=[5,1] and r2=[0,5] are not perpendicular. The inverse U of the matrix M=[r1,r2] has columns perpendicular to r2 and r1, so it must be of the form U=[xR(r2),yR(r1)]T for some scalars x and y. Find y1. 2. Vectors r1=[5,6] and r2=[24,20] are perpendicular. The inverse U of the matrix M=[r1,r2] has columns perpendicular to r2 and r1, so it must be of the form U=[xr1,yr2]T for some scalars x and y. Find x1