sinA=3/5什么意思
sina=3/5 \u7b49\u4e8e\u591a\u5c11\u5ea6\uff1f\uff1f\u5982\u679ca\u662f\u9510\u89d2\uff0ca\u224836.86989765\u00b0\u224837\u00b0
\u5982\u679c\u6ca1\u6709\u7ea6\u5b9a\uff0ca\u2248k\u00d7360\u00b0+36.86989765\u00b0\u6216
a\u2248k\u00d7360\u00b0+143.1301024\u00b0\uff0ck\u2208Z
\u53ef\u4ee5\u662f\u201437\u00b0\u6216143\u00b0
\u4e25\u8c28\u7684\u5199\u6cd5\u662fa =143\u00b0 +360\u00b0*k (\u662f360\u5269\u4ee5k\uff0ck\u4e3a\u6574\u6570\uff09\u6216a = \u201437\u00b0 + 360\u00b0*k (k\u4e3a\u6574\u6570\uff09
\u7edd\u5bf9\u662f\u8fd9\u6837
\u4f60\u5982\u679c\u662f\u9ad8\u4e2d\u7684360\u00b0\u4e5f\u53ef\u75282\u03c0\u4ee3\u66ff\uff0c\u4f46\u4ece\u4e66\u5199\u65b9\u5f0f\u4e0a\uff0c143\u00b0\u4e00\u822c\u4e0d\u548c\u03c0\u4e00\u8d77\u5199\uff0c\u7ed3\u679c\u91cc\u53ea\u80fd\u7edf\u4e00\u7528\u4e00\u79cd
绛旓細鏍规嵁姝ｅ鸡瀹氱悊寰楋細a/sinA=b/sinB 鍙緱锛歴inA=asinB/b=(3x鈭3/2)/5=3鈭3/10 鏍规嵁浣欏鸡瀹氱悊寰楋細c^2=a^2+b^2-2abcosB 鍙緱锛歝^2=9+25+15=49 鍗筹細c=7 鎵浠ユ湁锛歴inC=csinB/b=(7x鈭3/2)/5=7鈭3/10
绛旓細tana=sina/cosa=3 sina=3cosa sin²a+cos²a=1 (3cosa)²+cos²a=1 9cos²a+cos²a=1 10cos²a=1 cos²a=1/10 sinacosa =3cosa脳cosa =3cos²a =3脳1/10 =3/10
绛旓細sinA=3sinB cosC=-cos(A+B)=cosAcosB-sinAsinB=-2/3 sinC=鏍瑰彿5/3=sinAcosB+cosAsinB 鐢辨寮﹀畾鐞嗗彲寰 a=3b 鍐嶇敱浣欏鸡瀹氱悊c^2=a^2+b^2-2abcosC c^2=8b^2 c=2b鏍瑰彿2 sinC=2sinB鏍瑰彿2 蹇呴』鏈変竴鏉¤竟宸茬煡銆
绛旓細A涓轰笁瑙掑舰鍐呰.鎵浠inA>0 浠庤宑osA>0 cosA=鈭歔1-(sinA)^2]tanA=3 sinA/cosA=3 sinA/鈭歔1-(sinA)^2]=3 涓よ竟骞虫柟寰 (sinA)^2/[1-(sinA)^2]=9 (sinA)^2=9-9(sinA)^2 (sinA)^2=9/10 sinA=3鈭10/10
绛旓細sina=3/5 鍒檃=37搴.灏辨槸杈归暱鏄3,4,5鐨勭洿瑙掍笁瑙掑舰鐨勮.
绛旓細銆1銆sina=3cosa sin²a=9cos²a sin²a=9(1锛峴in²a)10sin²a=9 sin²a=9/10 鍥犱负a鏄涓夎薄闄愯锛屽垯sina<0 寰楋細sina=(3鈭10)/10 銆2銆慺(x)=1锛2(1锛峜os²x)锛2cosx f(x)=2cos²x锛2cosx锛1 璁撅細cosx=t锛屽垯锛歵鈭圼1/2锛1...
绛旓細鍦ㄢ柍ABC涓紝鈭sinA=3cosA锛屸埓3cos2A+cos2A=1锛屸埓cosA=12锛屾垨cosA=-12锛堣垗锛夛紝鈭0锛淎锛溝锛屸埓A=蟺3锛庢晠绛旀涓猴細蟺3锛
绛旓細=tanA/(1+tan^2A)=3/10 瑙ｆ硶2锛歵anA=3寰sinA=3cosA sinAcosA/(sin^2A+cos^2A)=3cos^2A/(9cos^2A+cos^2A)=3/10 瑙ｆ硶3锛歵anA=3寰梥inA=3cosA 鈭磗in^2A=9cos^2A 鈭磗in^2A+cos^2A=10cos^2A=1 鈭碿os^2A=1/10 鈭磗inAcosA=tanAcos^2A=3/10 瑙ｆ硶4锛歴inAcosA=(1/2)sin2A=tanA...
绛旓細sinacosa=3(cosa)^2,鍥犳鍙鏍规嵁鏉′欢(sina)^2+(cosa)^2=1鍜sina=3cosa杩欎袱涓潯浠惰仈绔嬫眰鍑(cosa)^2=0.1,鎵浠inacosa=3*0.1=0.3
绛旓細瑙ｏ細鈭礎鍦ㄧ鍥涜薄闄 鈭磗inA<0 鈭祎anA=3 鈭磗inA/cosA=3 ==>sinA=3cosA 鈭祍in²A+cos²A=1 鈭(3cosA)²+cos²A=1 ==>cos²A=1/10 鏁卻inA=-鈭(1-cos²A)=-鈭(1-1/10)=-3鈭10/10
