F.4 MATHS

1) sin (x - 10) = - cos 65

cos [90 - (x - 10)] = - cos 65

cos (100 - x) = - cos 65

cos (x - 100) = - cos 65

x - 100 = 115 or 245 (Note: - 100 < x - 100 < 260)

x = 215 or 345

2) 4b/√(ab3)

= 4b/(a1/2b3/2)

= 4a-1/2b-1/2

3) xx √(2/xy)

= √2 xx-1/2 y-1/2

後面兩題 "rationalize" 是要有理化（分母）。