第130页 - 苏科版九年级数学课课练答案（上下册）

$\frac {\sqrt{2}}{2}$

$3\sqrt{6}$

$\sqrt{2}-1$

$\frac {\sqrt{5}-1}{2}$

$解：原式=\frac {1}{2}-\frac {\sqrt{2}}{2}×\frac {\sqrt{2}}{2}+\frac {\sqrt{3}}{3}×1×\sqrt{3}$

$ =\frac {1}{2}-\frac {1}{2}+1$

$ =1$

$解：sin{15}°=sin(45°-30°)$

$ =sin{45}°cos{30}°-cos{45}°sin{30}°$

$ =\frac {\sqrt{2}}{2}×\frac {\sqrt{3}}{2}-\frac {\sqrt{2}}{2}×\frac {1}{2}$

$ =\frac {\sqrt{6}-\sqrt{2}}{4}$