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人気のある三角関数 >

証明する (2sec^2(x)-2tan^2(x))/(csc(x))=sin(2x)sec(x)

解

証明する

\frac{2 sec ^{2} ( x ) - 2 tan ^{2} ( x )}{csc ( x )} = sin (2 x) sec (x)

解

真

解答ステップ

\frac{2 sec ^{2} ( x ) - 2 tan ^{2} ( x )}{csc ( x )} = sin (2 x) sec (x)

左側を操作する

\frac{2 sec ^{2} ( x ) - 2 tan ^{2} ( x )}{csc ( x )}

サイン, コサインで表わす

\frac{2 sec ^{2} ( x ) - 2 tan ^{2} ( x )}{csc ( x )}

基本的な三角関数の公式を使用する:

sec (x) = \frac{1}{cos ( x )}

= \frac{2 ( \frac{1}{c o s ( x )} ) ^{2} - 2 tan ^{2} ( x )}{csc ( x )}

基本的な三角関数の公式を使用する:

tan (x) = \frac{sin ( x )}{cos ( x )}

= \frac{2 ( \frac{1}{c o s ( x )} ) ^{2} - 2 ( \frac{s i n ( x )}{c o s ( x )} ) ^{2}}{csc ( x )}

基本的な三角関数の公式を使用する:

csc (x) = \frac{1}{sin ( x )}

= \frac{2 ( \frac{1}{c o s ( x )} ) ^{2} - 2 ( \frac{s i n ( x )}{c o s ( x )} ) ^{2}}{\frac{1}{s i n ( x )}}

簡素化

\frac{2 ( \frac{1}{c o s ( x )} ) ^{2} - 2 ( \frac{s i n ( x )}{c o s ( x )} ) ^{2}}{\frac{1}{s i n ( x )}} : \frac{sin ( x ) ( 2 - 2 sin ^{2} ( x ) )}{cos ^{2} ( x )}

\frac{2 ( \frac{1}{c o s ( x )} ) ^{2} - 2 ( \frac{s i n ( x )}{c o s ( x )} ) ^{2}}{\frac{1}{s i n ( x )}}

分数の規則を適用する:

\frac{a}{\frac{b}{c}} = \frac{a \cdot c}{b}

= \frac{( 2 ( \frac{1}{c o s ( x )} ) ^{2} - 2 ( \frac{s i n ( x )}{c o s ( x )} ) ^{2} ) sin ( x )}{1}

2 (\frac{1}{cos ( x )})^{2} = \frac{2}{cos ^{2} ( x )}

2 (\frac{1}{cos ( x )})^{2}

(\frac{1}{cos ( x )})^{2} = \frac{1}{cos ^{2} ( x )}

(\frac{1}{cos ( x )})^{2}

指数の規則を適用する:

(\frac{a}{b})^{c} = \frac{a ^{c}}{b ^{c}}

= \frac{1 ^{2}}{cos ^{2} ( x )}

規則を適用

1^{a} = 1

1^{2} = 1

= \frac{1}{cos ^{2} ( x )}

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

分数を乗じる:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

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

数を乗じる:

1 \cdot 2 = 2

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

2 (\frac{sin ( x )}{cos ( x )})^{2} = \frac{2 sin ^{2} ( x )}{cos ^{2} ( x )}

2 (\frac{sin ( x )}{cos ( x )})^{2}

(\frac{sin ( x )}{cos ( x )})^{2} = \frac{sin ^{2} ( x )}{cos ^{2} ( x )}

(\frac{sin ( x )}{cos ( x )})^{2}

指数の規則を適用する:

(\frac{a}{b})^{c} = \frac{a ^{c}}{b ^{c}}

= \frac{sin ^{2} ( x )}{cos ^{2} ( x )}

= 2 \cdot \frac{sin ^{2} ( x )}{cos ^{2} ( x )}

分数を乗じる:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{sin ^{2} ( x ) \cdot 2}{cos ^{2} ( x )}

= \frac{sin ( x ) ( \frac{2}{c o s ^{2} ( x )} - \frac{2 s i n ^{2} ( x )}{c o s ^{2} ( x )} )}{1}

分数を組み合わせる

\frac{2}{cos ^{2} ( x )} - \frac{2 sin ^{2} ( x )}{cos ^{2} ( x )} : \frac{2 - 2 sin ^{2} ( x )}{cos ^{2} ( x )}

規則を適用

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{2 - 2 sin ^{2} ( x )}{cos ^{2} ( x )}

= \frac{( \frac{- 2 s i n ^{2} ( x ) + 2}{c o s ^{2} ( x )} ) sin ( x )}{1}

括弧を削除する:

(a) = a

= \frac{\frac{2 - s i n ^{2} ( x ) \cdot 2}{c o s ^{2} ( x )} sin ( x )}{1}

乗じる

\frac{2 - sin ^{2} ( x ) \cdot 2}{cos ^{2} ( x )} sin (x) : \frac{sin ( x ) ( - 2 sin ^{2} ( x ) + 2 )}{cos ^{2} ( x )}

\frac{2 - sin ^{2} ( x ) \cdot 2}{cos ^{2} ( x )} sin (x)

分数を乗じる:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{( 2 - sin ^{2} ( x ) \cdot 2 ) sin ( x )}{cos ^{2} ( x )}

= \frac{\frac{s i n ( x ) ( - 2 s i n ^{2} ( x ) + 2 )}{c o s ^{2} ( x )}}{1}

分数の規則を適用する:

\frac{a}{1} = a

= \frac{( 2 - sin ^{2} ( x ) \cdot 2 ) sin ( x )}{cos ^{2} ( x )}

= \frac{sin ( x ) ( 2 - 2 sin ^{2} ( x ) )}{cos ^{2} ( x )}

= \frac{( 2 - 2 sin ^{2} ( x ) ) sin ( x )}{cos ^{2} ( x )}

三角関数の公式を使用して書き換える

\frac{( 2 - 2 sin ^{2} ( x ) ) sin ( x )}{cos ^{2} ( x )}

ピタゴラスの公式を使用する:

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

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

= \frac{( 2 - 2 sin ^{2} ( x ) ) sin ( x )}{1 - sin ^{2} ( x )}

簡素化

\frac{( 2 - 2 sin ^{2} ( x ) ) sin ( x )}{1 - sin ^{2} ( x )} : 2 sin (x)

\frac{( 2 - 2 sin ^{2} ( x ) ) sin ( x )}{1 - sin ^{2} ( x )}

因数

2 - 2 sin^{2} (x) : 2 (1 - sin^{2} (x))

2 - 2 sin^{2} (x)

書き換え

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

共通項をくくり出す

2

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

= \frac{2 ( 1 - sin ^{2} ( x ) ) sin ( x )}{1 - sin ^{2} ( x )}

共通因数を約分する:

1 - sin^{2} (x)

= 2 sin (x)

= 2 sin (x)

= 2 sin (x)

右側を操作する

sin (2 x) sec (x)

サイン, コサインで表わす

sec (x) sin (2 x)

基本的な三角関数の公式を使用する:

sec (x) = \frac{1}{cos ( x )}

= \frac{1}{cos ( x )} sin (2 x)

簡素化

\frac{1}{cos ( x )} sin (2 x) : \frac{sin ( 2 x )}{cos ( x )}

\frac{1}{cos ( x )} sin (2 x)

分数を乗じる:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{1 \cdot sin ( 2 x )}{cos ( x )}

乗算:

1 \cdot sin (2 x) = sin (2 x)

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

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

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

三角関数の公式を使用して書き換える

\frac{sin ( 2 x )}{cos ( x )}

2倍角の公式を使用:

sin (2 x) = 2 sin (x) cos (x)

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

共通因数を約分する:

cos (x)

= 2 sin (x)

= 2 sin (x)

両辺を同じ形式にできることを証明した

\Rightarrow 真

人気の例

証明する sin(2α)=2sin(α)cos(α)

p ro v e sin (2 α) = 2 sin (α) cos (α)

証明する (1+csc(x))(1+csc(-x))=-cot^2(x)

p ro v e (1 + csc (x)) (1 + csc (- x)) = - cot^{2} (x)

証明する cos(0)-sec(0)=-sin(0)tan(0)

p ro v e cos (0) - sec (0) = - sin (0) tan (0)

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p ro v e tan (\frac{π}{6}) = \frac{1}{3}

証明する cos(4a)=1-8sin^2(a)cos^2(a)

p ro v e cos (4 a) = 1 - 8 sin^{2} (a) cos^{2} (a)