The trace of a matrix is the sum a + d of its diagonal entries. What can you say about...

The trace of a matrix is the sum a + d of its diagonal entries. What can you say about the trace of a 2 × 2 matrix that represents a(n)

a. orthogonal projection b. reflection about a line c. rotation d. (horizontal or vertical) shear. In three cases, give the exact value of the trace, and in one case, give an interval of possible values.