1 and (a, 9) are substituted into y = 3 x, that is, 9 = 3 a, and a=2 is obtained.

Tan2π/6=tanπ/3= radical number 3

2, b, that's not necessary. Explanation: Inevitability, "y=f(x) is odd function" is symmetrical about the origin, plus absolute value, and symmetrical about Y axis. But the image of y=|f(x)| may not pass through the origin on the Y axis, so "y = f (x)' is not odd function. Not enough.

3. A quarter of the period is π/6, so the period is 2π/3, so w=3.

I hope it will help the landlord ~ ~