中四數學20points!!!

9.tan150°xsin300°
=tan(180°-30°) x sin (360°-60°)
=tan(-30°) x sin(-60°)
= -1/(√3)x -(√3)/2
=1/2


10.sin﹫=(√3)/2
﹫=60° or (180°-60°)
﹫=60° or 120°


11.tan﹫=-1
﹫= -45°
﹫=(180°-45°) or( 360°-45°)
﹫=135° or 315°

12.
2sin﹫-1 = 0
2sin﹫=1
sin﹫=1/2
﹫= 30.0° or 150.0°
13.
2cos﹫+√3 = 0
2cos﹫= -√3
cos﹫= -(√3)/2
﹫= -30°
﹫= (180°-30°) or (180°+30°)
= 150.0° or 210.0°

14. tan﹫= -9/40

cos﹫> 0 and tan﹫< 0
therefore: 270°< ﹫ <360°
sin﹫< 0

sin﹫=-9/ √(9^2 + 40 ^ 2 )
= -9/ √(81+1600)
= -9/ √1681
= -9/ 41

sin﹫/cos﹫ = tan﹫
cos﹫ = sin﹫/tan﹫
cos﹫ = (-9/ 41) / (-9/40)
= 40/41