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1、1,1+1= ?,2,2-28. ,3, . . .,4,(1) m5.5 30 (m0.1 )., ,5, .,1. , : a2+b2=c2,a,b,c, ,6, .,2. ,A+B=90 :,7,3. ,a,b,c,(1)sinA=,(2)cosA=,(3)tanA=,=,=,=,8,(1)sinA=,(2)cosA=,(3)tanA=,4.A ,( ), .,9,(1) m5.5 30 (m0.1 )., , (- ),10, AB=,=, 6.4 m,: 6.4 3.2 ., cosA=,sin30=,BC=sin30AB,BC=,6.4 = 3.2 m, A=30 AC=5.5m
2、BCACABC ABC AB BC .,:,11,2-: RtABC C=90 AC= BC= .,A,C,B, :, tanA = = =, A =60,B=90 - A =90 - 60 =30,AB=2AC=2,A+B=90,12, .,13,1. RtABC C=90abc - ABC (1)c=10, A =30o (3)a=4, c=5,., ,a,b,c,a,14, . (1) . (2) ., , ,15,(1) :,a2 +b2 =c2 ( ),(2) :,A+B=90,(3) :, , ( sin A= = ),A, ( cosA= = ),A, (tanA= = ),A,16, 103- 1-2- ,17, ,