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1、弧形面积计算题:已知弧形ABC,其弦长L=3.24; 矢高h=0.39.求:弧形ABC的面积。
2、解:先求弧半径R 。
3、在直角三角形⊿OKC中,R2=(L/2)2 (R – h)2=R2-2hR h2 L2 / 4.得:R = ( h2 L2/4) / 2h =h / 2 L2 / 8h = 0.39 / 2 3.242 /( 8×0.39) = 3.559615385. ∠BOC = arcsin(L/2)/R = arcsin1.62/3.559615385 = 27.07171274°. 园心角∠AOC = 2∠BOC = 2×27.07171274°= 54.14342548°.再求扇形ABCO面积:扇形ABCO面积 = 3.1416 R2×54.14342548°/360°= 5.986862047.弧形ABC的面积 = 扇形ABCO面积 - 三角形⊿AOC面积 = 5.986862047 – L(R-h)/2 = 5.986862047 – 3.24×(3.559615385–0.39)/2 = 0.852085123.(画好的图复制不过来) 弧形ABC的面积 = 扇形ABCO面积 - 三角形⊿AOC面积 = 5.986862047 – L(R-h)/2 = 5.986862047 – 3.24×(3.559615385–0.39)/2 = 0.852085123. 弧长 = 园周长×园心角∠AOC / 360° = 2×3.1416 R×54.14342548°/360° = 2×3.1416 ×3.559615385×54.14342548°/360° = 3.363769059.长度12,高度1米求,弧形面积。
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