解答
cot(−5π)−sec(x)=1.5
解答
x=1.92586…+2πn,x=−1.92586…+2πn
+1
度数
x=110.34419…∘+360∘n,x=−110.34419…∘+360∘n求解步骤
cot(−5π)−sec(x)=1.5
cot(−5π)=−20(310+52)5−5
cot(−5π)
利用以下特性:cot(−x)=−cot(x)cot(−5π)=−cot(5π)=−cot(5π)
使用三角恒等式改写:cot(5π)=20(310+52)5−5
cot(5π)
使用三角恒等式改写:sin(5π)cos(5π)
cot(5π)
使用基本三角恒等式: cot(x)=sin(x)cos(x)=sin(5π)cos(5π)
=sin(5π)cos(5π)
使用三角恒等式改写:cos(5π)=45+1
cos(5π)
显示:cos(5π)−sin(10π)=21
使用以下积化和差公式: 2sin(x)cos(y)=sin(x+y)−sin(x−y)2cos(5π)sin(10π)=sin(103π)−sin(10π)
显示:2cos(5π)sin(10π)=21
使用倍角公式: sin(2x)=2sin(x)cos(x)sin(52π)=2sin(5π)cos(5π)sin(52π)sin(5π)=4sin(5π)sin(10π)cos(5π)cos(10π)
两边除以 sin(5π)sin(52π)=4sin(10π)cos(5π)cos(10π)
利用以下特性: sin(x)=cos(2π−x)sin(52π)=cos(2π−52π)cos(2π−52π)=4sin(10π)cos(5π)cos(10π)
cos(10π)=4sin(10π)cos(5π)cos(10π)
两边除以 cos(10π)1=4sin(10π)cos(5π)
两边除以 221=2sin(10π)cos(5π)
代入 21=2sin(10π)cos(5π)21=sin(103π)−sin(10π)
sin(103π)=cos(2π−103π)21=cos(2π−103π)−sin(10π)
21=cos(5π)−sin(10π)
显示:cos(5π)+sin(10π)=45
使用因式分解法则:a2−b2=(a+b)(a−b)a=cos(5π)+sin(10π)(cos(5π)+sin(10π))2−(cos(5π)−sin(10π))2=((cos(5π)+sin(10π))+(cos(5π)−sin(10π)))((cos(5π)+sin(10π))−(cos(5π)−sin(10π)))
整理后得(cos(5π)+sin(10π))2−(cos(5π)−sin(10π))2=2(2cos(5π)sin(10π))
显示:2cos(5π)sin(10π)=21
使用倍角公式: sin(2x)=2sin(x)cos(x)sin(52π)=2sin(5π)cos(5π)sin(52π)sin(5π)=4sin(5π)sin(10π)cos(5π)cos(10π)
两边除以 sin(5π)sin(52π)=4sin(10π)cos(5π)cos(10π)
利用以下特性: sin(x)=cos(2π−x)sin(52π)=cos(2π−52π)cos(2π−52π)=4sin(10π)cos(5π)cos(10π)
cos(10π)=4sin(10π)cos(5π)cos(10π)
两边除以 cos(10π)1=4sin(10π)cos(5π)
两边除以 221=2sin(10π)cos(5π)
代入 2cos(5π)sin(10π)=21(cos(5π)+sin(10π))2−(cos(5π)−sin(10π))2=1
代入 cos(5π)−sin(10π)=21(cos(5π)+sin(10π))2−(21)2=1
整理后得(cos(5π)+sin(10π))2−41=1
两边加上 41(cos(5π)+sin(10π))2−41+41=1+41
整理后得(cos(5π)+sin(10π))2=45
在两侧开平方cos(5π)+sin(10π)=±45
cos(5π)不能为负sin(10π)不能为负cos(5π)+sin(10π)=45
以下方程式相加cos(5π)+sin(10π)=25((cos(5π)+sin(10π))+(cos(5π)−sin(10π)))=(25+21)
整理后得cos(5π)=45+1
=45+1
使用三角恒等式改写:sin(5π)=425−5
sin(5π)
显示:cos(5π)−sin(10π)=21
使用以下积化和差公式: 2sin(x)cos(y)=sin(x+y)−sin(x−y)2cos(5π)sin(10π)=sin(103π)−sin(10π)
显示:2cos(5π)sin(10π)=21
使用倍角公式: sin(2x)=2sin(x)cos(x)sin(52π)=2sin(5π)cos(5π)sin(52π)sin(5π)=4sin(5π)sin(10π)cos(5π)cos(10π)
两边除以 sin(5π)sin(52π)=4sin(10π)cos(5π)cos(10π)
利用以下特性: sin(x)=cos(2π−x)sin(52π)=cos(2π−52π)cos(2π−52π)=4sin(10π)cos(5π)cos(10π)
cos(10π)=4sin(10π)cos(5π)cos(10π)
两边除以 cos(10π)1=4sin(10π)cos(5π)
两边除以 221=2sin(10π)cos(5π)
代入 21=2sin(10π)cos(5π)21=sin(103π)−sin(10π)
sin(103π)=cos(2π−103π)21=cos(2π−103π)−sin(10π)
21=cos(5π)−sin(10π)
显示:cos(5π)+sin(10π)=45
使用因式分解法则:a2−b2=(a+b)(a−b)a=cos(5π)+sin(10π)(cos(5π)+sin(10π))2−(cos(5π)−sin(10π))2=((cos(5π)+sin(10π))+(cos(5π)−sin(10π)))((cos(5π)+sin(10π))−(cos(5π)−sin(10π)))
整理后得(cos(5π)+sin(10π))2−(cos(5π)−sin(10π))2=2(2cos(5π)sin(10π))
显示:2cos(5π)sin(10π)=21
使用倍角公式: sin(2x)=2sin(x)cos(x)sin(52π)=2sin(5π)cos(5π)sin(52π)sin(5π)=4sin(5π)sin(10π)cos(5π)cos(10π)
两边除以 sin(5π)sin(52π)=4sin(10π)cos(5π)cos(10π)
利用以下特性: sin(x)=cos(2π−x)sin(52π)=cos(2π−52π)cos(2π−52π)=4sin(10π)cos(5π)cos(10π)
cos(10π)=4sin(10π)cos(5π)cos(10π)
两边除以 cos(10π)1=4sin(10π)cos(5π)
两边除以 221=2sin(10π)cos(5π)
代入 2cos(5π)sin(10π)=21(cos(5π)+sin(10π))2−(cos(5π)−sin(10π))2=1
代入 cos(5π)−sin(10π)=21(cos(5π)+sin(10π))2−(21)2=1
整理后得(cos(5π)+sin(10π))2−41=1
两边加上 41(cos(5π)+sin(10π))2−41+41=1+41
整理后得(cos(5π)+sin(10π))2=45
在两侧开平方cos(5π)+sin(10π)=±45
cos(5π)不能为负sin(10π)不能为负cos(5π)+sin(10π)=45
以下方程式相加cos(5π)+sin(10π)=25((cos(5π)+sin(10π))+(cos(5π)−sin(10π)))=(25+21)
整理后得cos(5π)=45+1
两边进行平方(cos(5π))2=(45+1)2
利用以下特性: sin2(x)=1−cos2(x)sin2(5π)=1−cos2(5π)
代入 cos(5π)=45+1sin2(5π)=1−(45+1)2
整理后得sin2(5π)=85−5
在两侧开平方sin(5π)=±85−5
sin(5π)不能为负sin(5π)=85−5
整理后得sin(5π)=225−5
=225−5
225−5=425−5
225−5
25−5=25−5
25−5
使用根式运算法则: nba=nbna, 假定 a≥0,b≥0=25−5
=225−5
使用分式法则: acb=c⋅ab=2⋅25−5
225−5有理化:425−5
225−5
乘以共轭根式 22=2⋅225−52
2⋅22=4
2⋅22
使用指数法则: ab⋅ac=ab+c222=2⋅221⋅221=21+21+21=21+21+21
同类项相加:21+21=2⋅21=21+2⋅21
2⋅21=1
2⋅21
分式相乘: a⋅cb=ca⋅b=21⋅2
约分:2=1
=21+1
数字相加:1+1=2=22
22=4=4
=425−5
=425−5
=425−5
=425−545+1
化简 425−545+1:20(310+52)5−5
425−545+1
分式相除: dcba=b⋅ca⋅d=425−5(5+1)⋅4
约分:4=25−55+1
25−55+1有理化:20(310+52)5−5
25−55+1
乘以共轭根式 22=25−52(5+1)2
25−52=25−5
25−52
使用根式运算法则: aa=a22=2=25−5
=25−52(5+1)
乘以共轭根式 5−55−5=25−55−52(5+1)5−5
25−55−5=10−25
25−55−5
使用根式运算法则: aa=a5−55−5=5−5=2(5−5)
使用分配律: a(b−c)=ab−aca=2,b=5,c=5=2⋅5−25
数字相乘:2⋅5=10=10−25
=10−252(5+1)5−5
因式分解出通项 −2:−2(5−5)
−25+10
将 10 改写为 2⋅5=−25+2⋅5
因式分解出通项 −2=−2(5−5)
=−2(5−5)2(5+1)5−5
消掉 −2(5−5)2(5+1)5−5:2(5−5)2(5+1)5−5
−2(5−5)2(5+1)5−5
5−5=−(5−5)=−−2(5−5)2(1+5)5−5
整理后得=2(5−5)2(5+1)5−5
=2(5−5)2(5+1)5−5
乘以共轭根式 5+55+5=2(5−5)(5+5)2(5+1)5−5(5+5)
2(5+1)5−5(5+5)=6105−5+1025−5
2(5+1)5−5(5+5)
=2(5+1)(5+5)5−5
乘开 (5+1)(5+5):65+10
(5+1)(5+5)
使用 FOIL 方法: (a+b)(c+d)=ac+ad+bc+bda=5,b=1,c=5,d=5=5⋅5+55+1⋅5+1⋅5
=55+55+1⋅5+1⋅5
化简 55+55+1⋅5+1⋅5:65+10
55+55+1⋅5+1⋅5
同类项相加:55+1⋅5=65=65+55+1⋅5
使用根式运算法则: aa=a55=5=65+5+1⋅5
数字相乘:1⋅5=5=65+5+5
数字相加:5+5=10=65+10
=65+10
=25−5(65+10)
乘开 25−5(65+10):6105−5+1025−5
25−5(65+10)
使用分配律: a(b+c)=ab+aca=25−5,b=65,c=10=25−5⋅65+25−5⋅10
=6255−5+1025−5
6255−5=6105−5
6255−5
使用根式运算法则: ab=a⋅b255−5=2⋅5(5−5)=62⋅5(5−5)
数字相乘:2⋅5=10=610(5−5)
使用根式运算法则: nab=nanb, 假定 a≥0,b≥010(5−5)=105−5=6105−5
=6105−5+1025−5
=6105−5+1025−5
2(5−5)(5+5)=40
2(5−5)(5+5)
乘开 (5−5)(5+5):20
(5−5)(5+5)
使用平方差公式: (a−b)(a+b)=a2−b2a=5,b=5=52−(5)2
化简 52−(5)2:20
52−(5)2
52=25
52
52=25=25
(5)2=5
(5)2
使用根式运算法则: a=a21=(521)2
使用指数法则: (ab)c=abc=521⋅2
21⋅2=1
21⋅2
分式相乘: a⋅cb=ca⋅b=21⋅2
约分:2=1
=5
=25−5
数字相减:25−5=20=20
=20
=2⋅20
乘开 2⋅20:40
2⋅20
打开括号=2⋅20
数字相乘:2⋅20=40=40
=40
=406105−5+1025−5
分解 6105−5+1025−5:25−5(310+52)
6105−5+1025−5
改写为=3⋅25−510+5⋅25−52
因式分解出通项 25−5=25−5(310+52)
=4025−5(310+52)
约分:2=20(310+52)5−5
=20(310+52)5−5
=20(310+52)5−5
=−20(310+52)5−5
−20(310+52)5−5−sec(x)=1.5
将 20(310+52)5−5到右边
−20(310+52)5−5−sec(x)=1.5
两边加上 20(310+52)5−5−20(310+52)5−5−sec(x)+20(310+52)5−5=1.5+20(310+52)5−5
化简
−20(310+52)5−5−sec(x)+20(310+52)5−5=1.5+20(310+52)5−5
化简 −20(310+52)5−5−sec(x)+20(310+52)5−5:−sec(x)
−20(310+52)5−5−sec(x)+20(310+52)5−5
同类项相加:−20(310+52)5−5+20(310+52)5−5=0
=−sec(x)
化简 1.5+20(310+52)5−5:2.87638…
1.5+20(310+52)5−5
20(310+52)5−5=2016.55790…5−5
20(310+52)5−5
310=9.48683…
310
转换为小数形式10=3.16227…=3⋅3.16227…
数字相乘:3⋅3.16227…=9.48683…=9.48683…
52=7.07106…
52
转换为小数形式2=1.41421…=5⋅1.41421…
数字相乘:5⋅1.41421…=7.07106…=7.07106…
=20(7.07106…+9.48683…)5−5
数字相加:9.48683…+7.07106…=16.55790…=2016.55790…5−5
=1.5+2016.55790…5−5
2016.55790…5−5=1.37638…
2016.55790…5−5
转换为小数形式5−5=1.66250…=201.66250…⋅16.55790…
数字相乘:16.55790…⋅1.66250…=27.52763…=2027.52763…
数字相除:2027.52763…=1.37638…=1.37638…
=1.5+1.37638…
数字相加:1.5+1.37638…=2.87638…=2.87638…
−sec(x)=2.87638…
−sec(x)=2.87638…
−sec(x)=2.87638…
两边除以 −1
−sec(x)=2.87638…
两边除以 −1−1−sec(x)=−12.87638…
化简sec(x)=−2.87638…
sec(x)=−2.87638…
使用反三角函数性质
sec(x)=−2.87638…
sec(x)=−2.87638…的通解sec(x)=−a⇒x=arcsec(−a)+2πn,x=−arcsec(−a)+2πnx=arcsec(−2.87638…)+2πn,x=−arcsec(−2.87638…)+2πn
x=arcsec(−2.87638…)+2πn,x=−arcsec(−2.87638…)+2πn
以小数形式表示解x=1.92586…+2πn,x=−1.92586…+2πn