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第二十六章　解直角三角形
26. 2 銳角三角函數的計算
INCLUDEPICTURE"復習回顧.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\復習回顧.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\復習回顧.tif" \* MERGEFORMATINET
1．用計算器求－53，按鍵的順序正確的是(　　)
2．用四舍五入法對0.060 45取近似值，錯誤的是(　　)
A．0.1(精確到0.1) B．0.06(精確到百分位)
C．0.061(精確到千分位) D．0.060 5(精確到0.000 1)
3．在下面的表中，填出 30°，45°，60°角的正弦值、余弦值和正切值．
30° 45° 60°
sin α
cos α
tan α
INCLUDEPICTURE"預習效果檢測.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\預習效果檢測.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\預習效果檢測.tif" \* MERGEFORMATINET
1．用計算器計算sin 24°的值，以下按鍵順序正確的是(　　)
A. B.
C. D.
2．如圖，一座廠房屋頂人字架的跨度AC＝12 m，上弦AB＝BC，∠BAC＝25°.若用科學計算器求上弦AB的長，則下列按鍵順序正確的是(　　)
INCLUDEPICTURE"image3324.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3324.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3324.tif" \* MERGEFORMATINET
A. 　 B.
C. D.
3．用科學計算器計算：＋3tan 56°(結果精確到0.01)．
INCLUDEPICTURE"課堂導學.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\課堂導學.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\課堂導學.tif" \* MERGEFORMATINET
INCLUDEPICTURE"W21.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\W21.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\W21.tif" \* MERGEFORMATINET
知識點1 用計算器求三角函數值INCLUDEPICTURE"L1.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\L1.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\L1.tif" \* MERGEFORMATINET [2023威海一模利用科學計算器計算cos 35°，下列按鍵順序正確的是(　　)
A.INCLUDEPICTURE"image3336.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3336.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3336.tif" \* MERGEFORMATINET
B.INCLUDEPICTURE"image3337.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3337.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3337.tif" \* MERGEFORMATINET
C.INCLUDEPICTURE"image3338.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3338.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3338.tif" \* MERGEFORMATINET
D.INCLUDEPICTURE"image3339.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3339.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\image3339.tif" \* MERGEFORMATINET
變式1用計算器求下列各式的值(結果精確到0.000 1)：
(1)sin 47°；　　(2)sin 12°30′；
(3)cos 25°18′；(4)sin 18°＋cos 55°－tan 59°.
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
知識點2 已知三角函數值用計算器求角度
INCLUDEPICTURE"L2.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\L2.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\L2.tif" \* MERGEFORMATINET 已知sin A＝0.501 8，用計算器求∠A的度數．(結果精確到1″)
變式2利用我們數學課本上采用的科學計算器按順序依次輸入：，顯示屏顯示的結果為88.443 009 64.將這個數據精確到0.1后，下列說法正確的是(　　)
A．36.79°的正切函數值約為88.4
B．正切函數值為36.79的角約是88.4°
C．36°79′的正切函數值約為88.4
D．正切函數值為36.79的角約是88°4′
26. 2 銳角三角函數的計算
INCLUDEPICTURE"復習回顧.tif" INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\復習回顧.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\復習回顧.tif" \* MERGEFORMATINET
1．A　2.C
3.
30° 45° 60°
sinα
cosα
tanα 1
INCLUDEPICTURE"預習效果.tif" INCLUDEPICTURE "預習效果.tif" \* MERGEFORMAT INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\預習效果.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\預習效果.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\預習效果.tif" \* MERGEFORMATINET
1．A　2.A
3．解：＋3tan 56°≈5.568＋3×1.483＝5.568＋4.449≈10.02.
INCLUDEPICTURE"課堂導學.tif" INCLUDEPICTURE "課堂導學.tif" \* MERGEFORMAT INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\課堂導學.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\課堂導學.tif" \* MERGEFORMATINET INCLUDEPICTURE "D:\\課件\\九數JJ河北（北京）\\課堂導學.tif" \* MERGEFORMATINET
例1　A　變式1.解：(1)sin 47°≈0.731 4；
(2)sin 12°30′≈0.216 4；
(3)cos 25°18′≈0.904 1；
(4)sin 18°＋cos 55°－tan 59°≈－0.781 7.
例2　解：利用計算器可求得∠A的度數約為30°7′9″.
變式2.B

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