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人気のある三角関数 >

-9sin^2(x)-5cos(x)+5=0

解

- 9 sin^{2} (x) - 5 cos (x) + 5 = 0

解

x = 2 πn, x = 2.03135 \dots + 2 πn, x = - 2.03135 \dots + 2 πn

+1

度

x = 0^{\circ} + 36 0^{\circ} n, x = 116.38779 \dots^{\circ} + 36 0^{\circ} n, x = - 116.38779 \dots^{\circ} + 36 0^{\circ} n

解答ステップ

- 9 sin^{2} (x) - 5 cos (x) + 5 = 0

三角関数の公式を使用して書き換える

5 - 5 cos (x) - 9 sin^{2} (x)

ピタゴラスの公式を使用する:

cos^{2} (x) + sin^{2} (x) = 1

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

= 5 - 5 cos (x) - 9 (1 - cos^{2} (x))

簡素化

5 - 5 cos (x) - 9 (1 - cos^{2} (x)) : 9 cos^{2} (x) - 5 cos (x) - 4

5 - 5 cos (x) - 9 (1 - cos^{2} (x))

拡張

- 9 (1 - cos^{2} (x)) : - 9 + 9 cos^{2} (x)

- 9 (1 - cos^{2} (x))

分配法則を適用する:

a (b - c) = ab - a c

a = - 9, b = 1, c = cos^{2} (x)

= - 9 \cdot 1 - (- 9) cos^{2} (x)

マイナス・プラスの規則を適用する

- (- a) = a

= - 9 \cdot 1 + 9 cos^{2} (x)

数を乗じる:

9 \cdot 1 = 9

= - 9 + 9 cos^{2} (x)

= 5 - 5 cos (x) - 9 + 9 cos^{2} (x)

簡素化

5 - 5 cos (x) - 9 + 9 cos^{2} (x) : 9 cos^{2} (x) - 5 cos (x) - 4

5 - 5 cos (x) - 9 + 9 cos^{2} (x)

条件のようなグループ

= - 5 cos (x) + 9 cos^{2} (x) + 5 - 9

数を足す/引く:

5 - 9 = - 4

= 9 cos^{2} (x) - 5 cos (x) - 4

= 9 cos^{2} (x) - 5 cos (x) - 4

= 9 cos^{2} (x) - 5 cos (x) - 4

- 4 - 5 cos (x) + 9 cos^{2} (x) = 0

置換で解く

- 4 - 5 cos (x) + 9 cos^{2} (x) = 0

仮定:

cos (x) = u

- 4 - 5 u + 9 u^{2} = 0

- 4 - 5 u + 9 u^{2} = 0 : u = 1, u = - \frac{4}{9}

- 4 - 5 u + 9 u^{2} = 0

標準的な形式で書く

a x^{2} + b x + c = 0

9 u^{2} - 5 u - 4 = 0

解くとthe二次式

9 u^{2} - 5 u - 4 = 0

二次Equationの公式:

次の場合:

a = 9, b = - 5, c = - 4

u_{1, 2} = \frac{- ( - 5 ) \pm ( - 5 ) ^{2} - 4 \cdot 9 ( - 4 )}{2 \cdot 9}

u_{1, 2} = \frac{- ( - 5 ) \pm ( - 5 ) ^{2} - 4 \cdot 9 ( - 4 )}{2 \cdot 9}

(- 5)^{2} - 4 \cdot 9 (- 4) = 13

(- 5)^{2} - 4 \cdot 9 (- 4)

規則を適用

- (- a) = a

= (- 5)^{2} + 4 \cdot 9 \cdot 4

指数の規則を適用する:

n

が偶数であれば

(- a)^{n} = a^{n}

(- 5)^{2} = 5^{2}

= 5^{2} + 4 \cdot 9 \cdot 4

数を乗じる:

4 \cdot 9 \cdot 4 = 144

= 5^{2} + 144

5^{2} = 25

= 25 + 144

数を足す:

25 + 144 = 169

= 169

数を因数に分解する:

169 = 1 3^{2}

= 1 3^{2}

累乗根の規則を適用する:

n a^{n} = a

1 3^{2} = 13

= 13

u_{1, 2} = \frac{- ( - 5 ) \pm 13}{2 \cdot 9}

解を分離する

u_{1} = \frac{- ( - 5 ) + 13}{2 \cdot 9}, u_{2} = \frac{- ( - 5 ) - 13}{2 \cdot 9}

u = \frac{- ( - 5 ) + 13}{2 \cdot 9} : 1

\frac{- ( - 5 ) + 13}{2 \cdot 9}

規則を適用

- (- a) = a

= \frac{5 + 13}{2 \cdot 9}

数を足す:

5 + 13 = 18

= \frac{18}{2 \cdot 9}

数を乗じる:

2 \cdot 9 = 18

= \frac{18}{18}

規則を適用

\frac{a}{a} = 1

= 1

u = \frac{- ( - 5 ) - 13}{2 \cdot 9} : - \frac{4}{9}

\frac{- ( - 5 ) - 13}{2 \cdot 9}

規則を適用

- (- a) = a

= \frac{5 - 13}{2 \cdot 9}

数を引く:

5 - 13 = - 8

= \frac{- 8}{2 \cdot 9}

数を乗じる:

2 \cdot 9 = 18

= \frac{- 8}{18}

分数の規則を適用する:

\frac{- a}{b} = - \frac{a}{b}

= - \frac{8}{18}

共通因数を約分する:

2

= - \frac{4}{9}

二次equationの解:

u = 1, u = - \frac{4}{9}

代用を戻す

u = cos (x)

cos (x) = 1, cos (x) = - \frac{4}{9}

cos (x) = 1, cos (x) = - \frac{4}{9}

cos (x) = 1 : x = 2 πn

cos (x) = 1

以下の一般解

cos (x) = 1

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 = 0 + 2 πn

x = 0 + 2 πn

解く

x = 0 + 2 πn : x = 2 πn

x = 0 + 2 πn

0 + 2 πn = 2 πn

x = 2 πn

x = 2 πn

cos (x) = - \frac{4}{9} : x = arccos (- \frac{4}{9}) + 2 πn, x = - arccos (- \frac{4}{9}) + 2 πn

cos (x) = - \frac{4}{9}

三角関数の逆数プロパティを適用する

cos (x) = - \frac{4}{9}

以下の一般解

cos (x) = - \frac{4}{9}

cos (x) = - a \Rightarrow x = arccos (- a) + 2 πn, x = - arccos (- a) + 2 πn

x = arccos (- \frac{4}{9}) + 2 πn, x = - arccos (- \frac{4}{9}) + 2 πn

x = arccos (- \frac{4}{9}) + 2 πn, x = - arccos (- \frac{4}{9}) + 2 πn

すべての解を組み合わせる

x = 2 πn, x = arccos (- \frac{4}{9}) + 2 πn, x = - arccos (- \frac{4}{9}) + 2 πn

10進法形式で解を証明する

x = 2 πn, x = 2.03135 \dots + 2 πn, x = - 2.03135 \dots + 2 πn

グラフ

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