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Popolare Trigonometria >

dimostrare ((sec(θ)-tan(θ))^2+1)/(csc(θ)(sec(θ)-tan(θ)))=2tan(θ)

Soluzione

dimostrare

\frac{( sec ( θ ) - tan ( θ ) ) ^{2} + 1}{csc ( θ ) ( sec ( θ ) - tan ( θ ) )} = 2 tan (θ)

Soluzione

Vero

Fasi della soluzione

\frac{( sec ( θ ) - tan ( θ ) ) ^{2} + 1}{csc ( θ ) ( sec ( θ ) - tan ( θ ) )} = 2 tan (θ)

Manipolando il lato sinistro

\frac{( sec ( θ ) - tan ( θ ) ) ^{2} + 1}{csc ( θ ) ( sec ( θ ) - tan ( θ ) )}

Esprimere con sen e cos

\frac{( sec ( θ ) - tan ( θ ) ) ^{2} + 1}{( sec ( θ ) - tan ( θ ) ) csc ( θ )}

Usare l'identità trigonometrica di base:

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

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

Usare l'identità trigonometrica di base:

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

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

Usare l'identità trigonometrica di base:

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

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

Semplifica

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

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

Combinare le frazioni

\frac{1}{cos ( θ )} - \frac{sin ( θ )}{cos ( θ )} : \frac{1 - sin ( θ )}{cos ( θ )}

Applicare la regola

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

= \frac{1 - sin ( θ )}{cos ( θ )}

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

Combinare le frazioni

\frac{1}{cos ( θ )} - \frac{sin ( θ )}{cos ( θ )} : \frac{1 - sin ( θ )}{cos ( θ )}

Applicare la regola

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

= \frac{1 - sin ( θ )}{cos ( θ )}

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

Rimuovi le parentesi:

(a) = a

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

Moltiplicare

\frac{1 - sin ( θ )}{cos ( θ )} \cdot \frac{1}{sin ( θ )} : \frac{1 - sin ( θ )}{cos ( θ ) sin ( θ )}

\frac{1 - sin ( θ )}{cos ( θ )} \cdot \frac{1}{sin ( θ )}

Moltiplica le frazioni:

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

= \frac{( 1 - sin ( θ ) ) \cdot 1}{cos ( θ ) sin ( θ )}

(1 - sin (θ)) \cdot 1 = 1 - sin (θ)

(1 - sin (θ)) \cdot 1

Moltiplicare:

(1 - sin (θ)) \cdot 1 = (1 - sin (θ))

= (1 - sin (θ))

Rimuovi le parentesi:

(a) = a

= 1 - sin (θ)

= \frac{1 - sin ( θ )}{cos ( θ ) sin ( θ )}

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

Applica la regola degli esponenti:

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

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

Applica la regola delle frazioni:

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

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

Unisci

\frac{( 1 - sin ( θ ) ) ^{2}}{cos ^{2} ( θ )} + 1 : \frac{( - sin ( θ ) + 1 ) ^{2} + cos ^{2} ( θ )}{cos ^{2} ( θ )}

\frac{( 1 - sin ( θ ) ) ^{2}}{cos ^{2} ( θ )} + 1

Converti l'elemento in frazione:

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

= \frac{( 1 - sin ( θ ) ) ^{2}}{cos ^{2} ( θ )} + \frac{1 \cdot cos ^{2} ( θ )}{cos ^{2} ( θ )}

Poiché i denominatori sono uguali, combinare le frazioni:

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

= \frac{( 1 - sin ( θ ) ) ^{2} + 1 \cdot cos ^{2} ( θ )}{cos ^{2} ( θ )}

Moltiplicare:

1 \cdot cos^{2} (θ) = cos^{2} (θ)

= \frac{( - sin ( θ ) + 1 ) ^{2} + cos ^{2} ( θ )}{cos ^{2} ( θ )}

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

Moltiplicare

\frac{( 1 - sin ( θ ) ) ^{2} + cos ^{2} ( θ )}{cos ^{2} ( θ )} cos (θ) sin (θ) : \frac{sin ( θ ) ( cos ^{2} ( θ ) + ( - sin ( θ ) + 1 ) ^{2} )}{cos ( θ )}

\frac{( 1 - sin ( θ ) ) ^{2} + cos ^{2} ( θ )}{cos ^{2} ( θ )} cos (θ) sin (θ)

Moltiplica le frazioni:

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

= \frac{( ( 1 - sin ( θ ) ) ^{2} + cos ^{2} ( θ ) ) cos ( θ ) sin ( θ )}{cos ^{2} ( θ )}

Cancella il fattore comune:

cos (θ)

= \frac{sin ( θ ) ( cos ^{2} ( θ ) + ( - sin ( θ ) + 1 ) ^{2} )}{cos ( θ )}

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

Applica la regola delle frazioni:

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

= \frac{sin ( θ ) ( cos ^{2} ( θ ) + ( - sin ( θ ) + 1 ) ^{2} )}{cos ( θ ) ( 1 - sin ( θ ) )}

= \frac{sin ( θ ) ( cos ^{2} ( θ ) + ( - sin ( θ ) + 1 ) ^{2} )}{cos ( θ ) ( 1 - sin ( θ ) )}

= \frac{( ( 1 - sin ( θ ) ) ^{2} + cos ^{2} ( θ ) ) sin ( θ )}{( 1 - sin ( θ ) ) cos ( θ )}

Riscrivere utilizzando identità trigonometriche

\frac{( ( 1 - sin ( θ ) ) ^{2} + cos ^{2} ( θ ) ) sin ( θ )}{( 1 - sin ( θ ) ) cos ( θ )}

Usa l'identità pitagorica:

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

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

= \frac{( ( 1 - sin ( θ ) ) ^{2} + 1 - sin ^{2} ( θ ) ) sin ( θ )}{( 1 - sin ( θ ) ) cos ( θ )}

Semplifica

\frac{( ( 1 - sin ( θ ) ) ^{2} + 1 - sin ^{2} ( θ ) ) sin ( θ )}{( 1 - sin ( θ ) ) cos ( θ )} : \frac{2 sin ( θ )}{cos ( θ )}

\frac{( ( 1 - sin ( θ ) ) ^{2} + 1 - sin ^{2} ( θ ) ) sin ( θ )}{( 1 - sin ( θ ) ) cos ( θ )}

Espandi

(1 - sin (θ))^{2} + 1 - sin^{2} (θ) : - 2 sin (θ) + 2

(1 - sin (θ))^{2} + 1 - sin^{2} (θ)

(1 - sin (θ))^{2} : 1 - 2 sin (θ) + sin^{2} (θ)

Applicare la formula del quadrato perfetto:

(a - b)^{2} = a^{2} - 2 ab + b^{2}

a = 1, b = sin (θ)

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

Semplifica

1^{2} - 2 \cdot 1 \cdot sin (θ) + sin^{2} (θ) : 1 - 2 sin (θ) + sin^{2} (θ)

1^{2} - 2 \cdot 1 \cdot sin (θ) + sin^{2} (θ)

Applicare la regola

1^{a} = 1

1^{2} = 1

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

Moltiplica i numeri:

2 \cdot 1 = 2

= 1 - 2 sin (θ) + sin^{2} (θ)

= 1 - 2 sin (θ) + sin^{2} (θ)

= 1 - 2 sin (θ) + sin^{2} (θ) + 1 - sin^{2} (θ)

Semplifica

1 - 2 sin (θ) + sin^{2} (θ) + 1 - sin^{2} (θ) : - 2 sin (θ) + 2

1 - 2 sin (θ) + sin^{2} (θ) + 1 - sin^{2} (θ)

Raggruppa termini simili

= - 2 sin (θ) + sin^{2} (θ) - sin^{2} (θ) + 1 + 1

Aggiungi elementi simili:

sin^{2} (θ) - sin^{2} (θ) = 0

= - 2 sin (θ) + 1 + 1

Aggiungi i numeri:

1 + 1 = 2

= - 2 sin (θ) + 2

= - 2 sin (θ) + 2

= \frac{sin ( θ ) ( - 2 sin ( θ ) + 2 )}{cos ( θ ) ( - sin ( θ ) + 1 )}

Fattorizza

- 2 sin (θ) + 2 : 2 (- sin (θ) + 1)

- 2 sin (θ) + 2

Riscrivi come

= - 2 sin (θ) + 2 \cdot 1

Fattorizzare dal termine comune

2

= 2 (- sin (θ) + 1)

= \frac{2 ( - sin ( θ ) + 1 ) sin ( θ )}{( 1 - sin ( θ ) ) cos ( θ )}

Cancella il fattore comune:

- sin (θ) + 1

= \frac{2 sin ( θ )}{cos ( θ )}

= \frac{2 sin ( θ )}{cos ( θ )}

= \frac{2 sin ( θ )}{cos ( θ )}

Riscrivere utilizzando identità trigonometriche

= 2 \cdot \frac{sin ( θ )}{cos ( θ )}

Usare l'identità trigonometrica di base:

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

2 tan (θ)

2 tan (θ)

Abbiamo mostrato che i due lati possono prendere la stessa forma

\Rightarrow Vero

Esempi popolari

dimostrare 2csc(2x)=sec(x)csc(x)

p ro v e 2 csc (2 x) = sec (x) csc (x)

dimostrare tan(x/2)=(sin(x))/(cos(x)+1)

p ro v e tan (\frac{x}{2}) = \frac{sin ( x )}{cos ( x ) + 1}

dimostrare (1-cos(θ))(1+sec(θ))=sin(θ)tan(θ)

p ro v e (1 - cos (θ)) (1 + sec (θ)) = sin (θ) tan (θ)

dimostrare tan(2t)=2sin(t)cos(t)sec(2t)

p ro v e tan (2 t) = 2 sin (t) cos (t) sec (2 t)

dimostrare tan^3(x)-tan(x)sec^2(x)=tan(-x)

p ro v e tan^{3} (x) - tan (x) sec^{2} (x) = tan (- x)