Which of the matrices in Exercises 1 through 4 orthogonal?

1.3 Vector Equations Vector – ordered lit of numbers − A matrix with only one column R – real numbers that appear as entries in the vectors Vectors in R 2 − R – (read “r-two) exponent 2 denotes that each vector contains two entries; the set of all 2ectors with two entries − two vectors in R are equal if and only if their corresponding entries are equal 4 7 − ≠ 7 4 2 − vectors in R are ordered pairs of real numbers Sum of Vectors (vector addition) 2 − given two vectors u and v in R , their sum in the vector u+v obtained by adding corresponding entries of u and v 2 1 + 2 3 − 1 + = = −2 5 −2 + 5 3 Scalar multiple