Analytic Geometry Answers

Which of the following statements are/is true ? Explain why the false one is false

A) If u= (u1,u2) with u(i) not equal to 0 for some 1< i < 2 ( both equal to i ) , then the unit vector in the direction of u is 1/ square root of u(1) squared + u(2) squared * (U(1), u(2)).

B) If u= (1,2,3) find the unit vector in the direction of u.

Which of this is not true?

a.\\(i \times i=j \times j=k \times k=0\\)

b.\\(\alpha \times \beta = \beta \times \alpha \\)

c.\\(\alpha \times \beta =- \beta \times \alpha \\)

d.\\(\alpha \times \beta \neq \beta \times \alpha \\)