1、 1 28.1 1 sin59 sin28 0cos 1 tan30 +tan60 =tan90 tan44 cot44 =1 A 1 B 2 C 3 D 4 2 a cos = 1 3 A 0 30 B 30 45 C 45 60 D 60 90 3 1 Rt ABC C=90 D BC DAC=30 BD=2 AB=2 3 AC A 3 B 2 2 C 3 D 3 2 3 4. Rt ABC C=90 a b c A B C A b=c cosA B b=a sinB C a=b tanB D b=c cotA 5 sin72 _ 6 tan25 42 _ 7 cos18 44 25 =_
2、 8 9 40m A C 31 D 72 1 31 = _= _ 2 27 = _= _ 3 Rt ABC BC=_ 1m 9 4 Rt ABD BC=_ 1m 5 CD=_BC=_ D C B A E D C B A 2 9. 1 sin42 31 2 cos33 18 24 3 tan55 10 10 1 sin =0.4771 1 2 cos =0.8451 1 3 tan =1.4106 1 11 ABC ACB=108 AC=10m AB 1cm 28.1 3 D C B A C D A A 5 sin 7 2 = 6 tan 2 5 + 4 2 6 0 = 7 0.9469846
3、59 8 1 EAC ACB 2 EAD ADB 3 67 4 79 5 BD 12 9 1 0.675804644 2 0.835743474 3 1.445081367 10 1 28 29 46 2 32 19 2 3 54 39 59 11 CD AB D ACD= 1 2 ACB=54 AB=2AD Rt ADC ADC=90 cos ACD= CD AC CD=AC cos ACD=10 cos54 10 0.59=6 cm sin ACD= AD AC AD=AC sin ACD=10 sin54 10 0.81=8 cm AB=2AD=16 cm S ABC= 1 2 AB CD= 1 2 cm 2
