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人気のある三角関数 >

solvefor x,4cos^3(x)=3cos(x)

解

解く

x, 4 cos^{3} (x) = 3 cos (x)

解

x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn, x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn, x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn

+1

度

x = 9 0^{\circ} + 36 0^{\circ} n, x = 27 0^{\circ} + 36 0^{\circ} n, x = 15 0^{\circ} + 36 0^{\circ} n, x = 21 0^{\circ} + 36 0^{\circ} n, x = 3 0^{\circ} + 36 0^{\circ} n, x = 33 0^{\circ} + 36 0^{\circ} n

解答ステップ

4 cos^{3} (x) = 3 cos (x)

置換で解く

4 cos^{3} (x) = 3 cos (x)

仮定:

cos (x) = u

4 u^{3} = 3 u

4 u^{3} = 3 u : u = 0, u = - \frac{3}{2}, u = \frac{3}{2}

4 u^{3} = 3 u

3 u

を左側に移動します

4 u^{3} = 3 u

両辺から

3 u

を引く

4 u^{3} - 3 u = 3 u - 3 u

簡素化

4 u^{3} - 3 u = 0

4 u^{3} - 3 u = 0

因数

4 u^{3} - 3 u : u (2 u + 3) (2 u - 3)

4 u^{3} - 3 u

共通項をくくり出す

u : u (4 u^{2} - 3)

4 u^{3} - 3 u

指数の規則を適用する:

a^{b + c} = a^{b} a^{c}

u^{3} = u^{2} u

= 4 u^{2} u - 3 u

共通項をくくり出す

u

= u (4 u^{2} - 3)

= u (4 u^{2} - 3)

因数

4 u^{2} - 3 : (2 u + 3) (2 u - 3)

4 u^{2} - 3

4 u^{2} - 3

を書き換え

(2 u)^{2} - (3)^{2}

4 u^{2} - 3

4

を書き換え

2^{2}

= 2^{2} u^{2} - 3

累乗根の規則を適用する:

a = (a)^{2}

3 = (3)^{2}

= 2^{2} u^{2} - (3)^{2}

指数の規則を適用する:

a^{m} b^{m} = (ab)^{m}

2^{2} u^{2} = (2 u)^{2}

= (2 u)^{2} - (3)^{2}

= (2 u)^{2} - (3)^{2}

2乗の差の公式を適用する:

x^{2} - y^{2} = (x + y) (x - y)

(2 u)^{2} - (3)^{2} = (2 u + 3) (2 u - 3)

= (2 u + 3) (2 u - 3)

= u (2 u + 3) (2 u - 3)

u (2 u + 3) (2 u - 3) = 0

零因子の原則を使用:

ab = 0

ならば

a = 0

または

b = 0

u = 0 or 2 u + 3 = 0 or 2 u - 3 = 0

解く

2 u + 3 = 0 : u = - \frac{3}{2}

2 u + 3 = 0

3

を右側に移動します

2 u + 3 = 0

両辺から

3

を引く

2 u + 3 - 3 = 0 - 3

簡素化

2 u = - 3

2 u = - 3

以下で両辺を割る

2

2 u = - 3

以下で両辺を割る

2

\frac{2 u}{2} = \frac{- 3}{2}

簡素化

u = - \frac{3}{2}

u = - \frac{3}{2}

解く

2 u - 3 = 0 : u = \frac{3}{2}

2 u - 3 = 0

3

を右側に移動します

2 u - 3 = 0

両辺に

3

を足す

2 u - 3 + 3 = 0 + 3

簡素化

2 u = 3

2 u = 3

以下で両辺を割る

2

2 u = 3

以下で両辺を割る

2

\frac{2 u}{2} = \frac{3}{2}

簡素化

u = \frac{3}{2}

u = \frac{3}{2}

解答は

u = 0, u = - \frac{3}{2}, u = \frac{3}{2}

代用を戻す

u = cos (x)

cos (x) = 0, cos (x) = - \frac{3}{2}, cos (x) = \frac{3}{2}

cos (x) = 0, cos (x) = - \frac{3}{2}, cos (x) = \frac{3}{2}

cos (x) = 0 : x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn

cos (x) = 0

以下の一般解

cos (x) = 0

cos (x)

2 πn

循環を含む周期性テーブル:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn

x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn

cos (x) = - \frac{3}{2} : x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn

cos (x) = - \frac{3}{2}

以下の一般解

cos (x) = - \frac{3}{2}

cos (x)

2 πn

循環を含む周期性テーブル:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn

x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn

cos (x) = \frac{3}{2} : x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn

cos (x) = \frac{3}{2}

以下の一般解

cos (x) = \frac{3}{2}

cos (x)

2 πn

循環を含む周期性テーブル:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn

x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn

すべての解を組み合わせる

x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn, x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn, x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn

グラフ

人気の例

cos^2(x)=2cos(x)-1

cos^{2} (x) = 2 cos (x) - 1

sqrt(11)sin(x+37.09)=1

11 sin (x + 37.0 9^{\circ}) = 1

cot^2(x)+3csc(x)+3=0

cot^{2} (x) + 3 csc (x) + 3 = 0

cos(2x)+cos(x)-1=0

cos (2 x) + cos (x) - 1 = 0

cos(2x)-1=-sin(2x)

cos (2 x) - 1 = - sin (2 x)