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28
锛?/p>
1
閿愯涓夎鍑芥暟锛?/p>
1
锛夊瀛︽
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1
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鍒濇浜嗚В閿愯涓夎鍑芥暟鐨勬剰涔夛紝
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2
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1
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Rt
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ABC
涓紝鈭?/p>
C=90
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A=30
掳锛?/p>
BC=10m
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鈥?/p>
姹?/p>
AB
2
銆佸鍥惧湪
Rt
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ABC
涓紝鈭?/p>
C=90
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A=30
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AB=20m
锛?/p>
鈥?/p>
姹?/p>
BC
銆愯嚜涓绘帰绌?/p>
銆?/p>
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銆佽嚜瀛﹁鏈?/p>
P74-76
鎬濊�冧笅鍒楅棶棰橈細
鎬濊�?/p>
1
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濡傛灉浣垮嚭姘村彛鐨勯珮搴︿负
50m
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锛?/p>
濡?/p>
鏋滀娇鍑烘按鍙ｇ殑楂樺害涓?/p>
a m
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锛?/p>
缁撹锛氱洿瑙掍笁瑙掑舰涓紝
30
掳瑙掔殑瀵硅竟涓庢枩杈圭殑姣斿�兼槸
鎬濊�?/p>
2
锛?/p>
鍦?/p>
Rt
鈻?/p>
ABC
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C=90
掳锛屸垹
A=45
掳锛屸垹
A
瀵硅竟涓庢枩杈?/p>
鐨勬瘮鍊兼槸涓�涓畾鍊煎悧锛?/p>
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濡傛灉鏄紝鏄灏戯紵
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45
掳瑙掔殑瀵硅竟涓庢枩杈圭殑姣斿�?/p>
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3
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鍦?/p>
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鈻?/p>
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B=60
掳锛屸垹
B
瀵硅竟涓庢枩杈圭殑
姣斿�兼槸涓�涓畾鍊煎悧锛?/p>
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60
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4
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A
鈥?/p>
B
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C
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=90
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A
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A
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A
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A
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5
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A
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A
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锛屽嵆
_________
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1
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2
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(2)
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Rt
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C=90
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3
锛?/p>
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ABC
涓紝鈭?/p>
C=90
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BC=2
锛?/p>
sinA=
2
3
锛屽垯杈?/p>
AC
鐨勯暱鏄?/p>
( )
A
锛?/p>
13 B
锛?/p>
3 C
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4
3
D
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5
4
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P
鐨勫潗鏍囨槸锛?/p>
a
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b
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sin
伪绛変簬锛?/p>
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A
锛?/p>
a
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B
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C
锛?/p>
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a
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__________________________________
_______________________________________________________________
銆愯寖渚嬬簿鏋愩�?/p>
1
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Rt
鈻?/p>
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0
锛?/p>
sinA=
5
3
,
姹?/p>
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.
2
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0
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CD
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D
鐐癸紝
AC=3
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BC=4
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姹?/p>
sinA
銆?/p>
sin
鈭?/p>
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.
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1
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ABC
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锛?/p>
鈭?/p>
C=90
0
锛?/p>
AC=5cm,BC=3cm,
鍒?/p>
sinA=______,sinB=________.
2
銆佸湪
Rt
鈻?/p>
ABC
涓紝鈭?/p>
C=90
0
锛屽鏋滃悇杈圭殑闀垮害閮芥墿澶?/p>
2
鍊嶏紝
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A
鐨勬寮﹀�硷紙
锛?/p>
A
銆佹墿澶т袱鍊?/p>
B
銆佺缉灏忎袱鍊?/p>
C
銆佹病鏈夊彉鍖?/p>
D
銆佷笉
鑳界‘瀹?/p>
3
銆?/p>
鍦?/p>
Rt
鈻?/p>
ABC
涓紝
鈭?/p>
C=90
0
锛?/p>
AB=15
锛?/p>
sinA=
3
1
锛?/p>
鍒?/p>
AC=_______
锛?/p>
S
鈻?/p>
ABC
=_______.
28
锛?/p>
1
閿愯涓夎鍑芥暟锛?/p>
2
锛夊瀛︽
B
C
A
B
C
A
B
C
A
D
C
B
A
鍥?/p>
2
鍥?/p>
1
5
13
4
3
C
A
C
B
B
A