18度的余弦值
18\u5ea6\u7684\u6b63\u5f26\u503c\u548c\u4f59\u5f26\u503c\u60a8\u597d\uff01
18\u5ea6\u7684\u6b63\u5f26\u503c\uff1a0.3090169
18\u5ea6\u7684\u4f59\u5f26\u503c\uff1a0.9510565
\u7cfb\u7edf\u81ea\u5e26\u7684\u8ba1\u7b97\u5668\u5c31\u53ef\u4ee5\u554a
"\u5f00\u59cb"-"\u7a0b\u5e8f"-"\u9644\u4ef6"-"\u8ba1\u7b97\u5668"
\u6253\u5f00\u8ba1\u7b97\u5668\u540e,\u70b9\u51fb"\u83dc\u5355"\u9009\u53d6"\u67e5\u770b"
\u5c31\u6709\u4e86..
\u52a0\u6cd5\uff1a3+2
\u51cf\u6cd5\uff1a3-2
\u4e58\u6cd5\uff1a3*2
\u9664\u6cd5\uff1a3/2
\u9636\u4e58\uff1a4! 4\u7684\u9636\u4e58
\u5e73\u65b9\uff1a4^2 4\u7684\u5e73\u65b9
\u7acb\u65b9\uff1a4^3 4\u7684\u7acb\u65b9
\u5f00\u5e73\u65b9\uff1a4^(1/2) 4\u7684\u5e73\u65b9\u6839
\u5f00\u7acb\u65b9\uff1a4^(1/3) 4\u7684\u7acb\u65b9\u6839
\u5012\u6570\uff1a1/4 4\u7684\u5012\u6570
\u5e42\u8fd0\u7b97\uff1a2^8 2\u76848\u6b21\u65b9
\u5e38\u7528\u5bf9\u6570\uff1alog(8) \u4ee510 \u4e3a\u5e958\u7684\u5bf9\u6570
\u4ee5\u81ea\u7136\u5e95\u6570\u4e3a\u5e95\u7684\u5bf9\u6570\uff1aln(8) \u4ee5e\u4e3a\u5e958\u7684\u5bf9\u6570
\u6c42\u5f27\u5ea6\u7684\u6b63\u5f26\uff1asin(10) 10\u5f27\u5ea6\u89d2\u6b63\u5f26\u503c
\u6c42\u5f27\u5ea6\u7684\u4f59\u5f26\uff1acos(10) 10\u5f27\u5ea6\u89d2\u4f59\u5f26\u503c
\u6c42\u5f27\u5ea6\u7684\u6b63\u5207\uff1atan(10) 10\u5f27\u5ea6\u89d2\u6b63\u5207\u503c
\u4e0a\u8ff0\u8fd0\u7b97\u7684\u6df7\u5408\u8fd0\u7b97\uff1alog((5+5)^2)-3+pi
\u5706\u5468\u7387pi=3.14159265
\u81ea\u7136\u5e95\u6570e=2.71828183
sin36\u00b0\uff1dcos54\u00b0
\u5373sin\uff082\u00d718\u00b0\uff09\uff1dcos\uff083\u00d718\u00b0\uff09
2sin18\u00b0cos18\u00b0\uff1d4(cos18\u00b0)^3\uff0d3cos18\u00b0
\u56e0\u4e3acos18\u00b0\u22600
\u6240\u4ee52sin18\u00b0\uff1d4(cos18\u00b0)^2\uff0d3
\u6574\u7406\u5f974(sin18\u00b0)\uff3e2\uff0b2sin18\u00b0\uff0d1\uff1d0
\u89e3\u5f97sin18\u00b0=\u221a(5-1 )/4\u22480.3090169
\u6269\u5c55\u8d44\u6599\uff1a
\u6b63\u5f26\u51fd\u6570
\u4e00\u822c\u7684\uff0c\u5728\u76f4\u89d2\u5750\u6807\u7cfb\u4e2d\uff0c\u7ed9\u5b9a\u5355\u4f4d\u5706\uff0c\u5bf9\u4efb\u610f\u89d2\u03b1\uff0c\u4f7f\u89d2\u03b1\u7684\u9876\u70b9\u4e0e\u539f\u70b9\u91cd\u5408\uff0c\u59cb\u8fb9\u4e0ex\u8f74\u975e\u8d1f\u534a\u8f74\u91cd\u5408\uff0c\u7ec8\u8fb9\u4e0e\u5355\u4f4d\u5706\u4ea4\u4e8e\u70b9P\uff08u\uff0cv\uff09\uff0c\u90a3\u4e48\u70b9P\u7684\u7eb5\u5750\u6807v\u53eb\u505a\u89d2\u03b1\u7684\u6b63\u5f26\u51fd\u6570\uff0c\u8bb0\u4f5cv=sin\u03b1\u3002
\u901a\u5e38\uff0c\u6211\u4eec\u7528x\u8868\u793a\u81ea\u53d8\u91cf\uff0c\u5373x\u8868\u793a\u89d2\u7684\u5927\u5c0f\uff0c\u7528y\u8868\u793a\u51fd\u6570\u503c\uff0c\u8fd9\u6837\u6211\u4eec\u5c31\u5b9a\u4e49\u4e86\u4efb\u610f\u89d2\u7684\u4e09\u89d2\u51fd\u6570y=sin x\uff0c\u5b83\u7684\u5b9a\u4e49\u57df\u4e3a\u5168\u4f53\u5b9e\u6570\uff0c\u503c\u57df\u4e3a[-1,1]\u3002
\u76f8\u5173\u516c\u5f0f
\u5e73\u65b9\u548c\u5173\u7cfb
\uff08sin\u03b1\uff09^2 +\uff08cos\u03b1\uff09^2=1
\u79ef\u7684\u5173\u7cfb
sin\u03b1 = tan\u03b1 \u00d7 cos\u03b1\uff08\u5373sin\u03b1 / cos\u03b1 = tan\u03b1 \uff09
cos\u03b1 = cot\u03b1 \u00d7 sin\u03b1 \uff08\u5373cos\u03b1 / sin\u03b1 = cot\u03b1\uff09
tan\u03b1 = sin\u03b1 \u00d7 sec\u03b1 (\u5373 tan\u03b1 / sin\u03b1 = sec\u03b1)
\u53c2\u8003\u8d44\u6599\uff1a\u767e\u5ea6\u767e\u79d1-\u6b63\u5f26
设sin18=x, cos36=cos2*18=1-2(sin18)^2=1-2x^2,(cos18)^2=1-x^2
sin36=2xcos18
sin18cos36+cos18sin36=cos36
x(1-2x^2) +2x(1-x^2)=1-2x^2
4x^3-2x^-3x+1=0
4x^3-2x^-2x-x+1=0 2x(2x^2-x-1)-(x-1)=0 2x(2x+1)(x-1)-(x-1)=0
(x-1)(4x+2x-1)=0
解此方程得:sin18=x=(-1+√5)/4 (x=(-1-√5)/4<0舍去)
级别:大师
3月18日 23:26 解:∵sin36°=cos54°
即sin(2×18°)=cos(3×18°)
2sin18°cos18°=4(cos18°)^3-3cos18°
∵cos18°≠0
∴2sin18°=4(cos18°)^2-3
整理得4(sin18°)^2+2sin18°-1=0
解得sin18°=(根号5-1)/4
解法2.令x = 18°
∴cos3x = sin2x
∴4(cosx)^3 - 3cosx = 2sinxcosx
∵cosx≠ 0
∴4(cosx)^2 - 3 = 2sinx
∴4sinx2 + 2sinx - 1 = 0,
又0 < sinx < 1
∴sinx = (√5 - 1)/4
即sin18° = (√5 - 1)/4.
解法3. 作顶角为36°、腰长为1 的等腰三角形ABC, BD为其底角B的平分线,设AD = x
则AD = BD = BC = x, DC = 1 - x.
由相似三角形得:x2 = 1 - x
∴x = (√ 5 - 1)/2
∴sin18° = x/2 = (√5 - 1)/4.
系统自带的计算器就可以啊
"开始"-"程序"-"附件"-"计算器"
打开计算器后,点击"菜单"选取"查看"
就有了..
加法:3+2
减法:3-2
乘法:3*2
除法:3/2
阶乘:4! 4的阶乘
平方:4^2 4的平方
立方:4^3 4的立方
开平方:4^(1/2) 4的平方根
开立方:4^(1/3) 4的立方根
倒数:1/4 4的倒数
幂运算:2^8 2的8次方
常用对数:log(8) 以10 为底8的对数
以自然底数为底的对数:ln(8) 以e为底8的对数
求弧度的正弦:sin(10) 10弧度角正弦值
求弧度的余弦:cos(10) 10弧度角余弦值
求弧度的正切:tan(10) 10弧度角正切值
上述运算的混合运算:log((5+5)^2)-3+pi
圆周率pi=3.14159265
自然底数e=2.71828183
参考资料:http://zhidao.baidu.com/question/8439548.html
0.95105651629515357211643933337938
在数学用表中可以查到
也可以利用计算器
你知道36度的余弦值怎么只用根式,加减乘除符号表达吗?
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