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(sin x * tan x) / (1 - cos x) - 1 = sec x

Show that left equals right.

 Feb 29, 2016

Best Answer 

 #1
avatar+26387 
+10

(sin x * tan x) / (1 - cos x) - 1 = sec x
Show that left equals right.

 

\(\begin{array}{rcll} \frac{ \sin{( x )} \cdot \tan{( x )} } { 1 - \cos{( x )} } - 1 & \overset{?}{=} & \sec {( x )} \qquad & | \qquad \sec {( x )} = \frac{1}{\cos {( x )}}\\\\ & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ \sin{( x )} \cdot \tan{( x )} } { 1 - \cos{( x )} } - 1 & \overset{?}{=} & \frac{1}{\cos {( x )}} \qquad & | \qquad \tan {( x )} = \frac{\sin {( x )} }{\cos {( x )}} \\\\ \frac{ \sin{( x )} \cdot \frac{\sin {( x )} }{\cos {( x )}} } { 1 - \cos{( x )} } - 1 & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ \sin^2{( x )} } { \cos {( x )}\cdot [ 1 - \cos{( x )} ]} - 1 & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ \sin^2{( x )} - \cos {( x )}\cdot [ 1 - \cos{( x )} ] } { \cos {( x )}\cdot [ 1 - \cos{( x )} ]} & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ \sin^2{( x )} - \cos {( x )} + \cos^2{( x )} } { \cos {( x )}\cdot [ 1 - \cos{( x )} ]} & \overset{?}{=} & \frac{1}{\cos {( x )}} \qquad & | \qquad \sin{( x )}^2 + \cos^2 {( x )} = 1 \\\\ \frac{ [ 1 - \cos {( x )} ] } { \cos {( x )}\cdot [ 1 - \cos{( x )} ]} & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ 1 } { \cos {( x )} } & = & \frac{1}{\cos {( x )}} \end{array}\)

 

laugh

 Mar 1, 2016
 #1
avatar+26387 
+10
Best Answer

(sin x * tan x) / (1 - cos x) - 1 = sec x
Show that left equals right.

 

\(\begin{array}{rcll} \frac{ \sin{( x )} \cdot \tan{( x )} } { 1 - \cos{( x )} } - 1 & \overset{?}{=} & \sec {( x )} \qquad & | \qquad \sec {( x )} = \frac{1}{\cos {( x )}}\\\\ & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ \sin{( x )} \cdot \tan{( x )} } { 1 - \cos{( x )} } - 1 & \overset{?}{=} & \frac{1}{\cos {( x )}} \qquad & | \qquad \tan {( x )} = \frac{\sin {( x )} }{\cos {( x )}} \\\\ \frac{ \sin{( x )} \cdot \frac{\sin {( x )} }{\cos {( x )}} } { 1 - \cos{( x )} } - 1 & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ \sin^2{( x )} } { \cos {( x )}\cdot [ 1 - \cos{( x )} ]} - 1 & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ \sin^2{( x )} - \cos {( x )}\cdot [ 1 - \cos{( x )} ] } { \cos {( x )}\cdot [ 1 - \cos{( x )} ]} & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ \sin^2{( x )} - \cos {( x )} + \cos^2{( x )} } { \cos {( x )}\cdot [ 1 - \cos{( x )} ]} & \overset{?}{=} & \frac{1}{\cos {( x )}} \qquad & | \qquad \sin{( x )}^2 + \cos^2 {( x )} = 1 \\\\ \frac{ [ 1 - \cos {( x )} ] } { \cos {( x )}\cdot [ 1 - \cos{( x )} ]} & \overset{?}{=} & \frac{1}{\cos {( x )}} \\\\ \frac{ 1 } { \cos {( x )} } & = & \frac{1}{\cos {( x )}} \end{array}\)

 

laugh

heureka Mar 1, 2016

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