CPM Homework Help : CCA2 Problem 12-5

Decide if each of the following statements are always true, sometimes true, or never true. If a statement is always true, justify how you know; if it is sometimes true, give the exact values of $x$ that make it true; and if it is never true, explain why it is never true.

$3x - 2 - 4(x + 1) = -x - 6$
Hint (a):
Simplify the part of the equation on the left side of the equals sign.
Does it equal the part on the right side?
Answer (a):
Always.

$3x - 5 = 2(x + 1) + x$
Hint (b):
Use the same method as part (a).

sin( $x$ ) $=$ cos( $\frac { \pi } { 2 }- x$ )
Hint (c):
Substitute values into the equations for x.
Are they always equal?
Answer (c):
Always.

tan( $x$ ) $= 1$
Hint (d):
Is this always true?
If not, what values of $x$ would make it true?