I encountered the above problem in

*Schaum’s Outlines of Linear Algebra 6th Ed (2017, McGraw-Hill) Chapter 7 - Inner Product Spaces, Orthogonality.*Using some particular values for

**and**

*u***, I proved that**

*v***and**

*a***must be real positive, and**

*d***is the conjugate of**

*b***. The solution indicates that**

*c***must also be positive, but i can't figure that out.**

*a.d-b.c*thanks for your help.