$(2)(7$ points$)$ Let and

$($a$)$ Find $Com{p}_{a}b.$

$($b$)$ Find $p=Pro{j}_{a}b.$

$($c$)$ Compute $v=b-p.$

$($d$)$ Show that $|{)}_a.$

$($In fact, it is always true that $b-Pro{j}_{a}b$ is orthogonal to $a-$ you ne