(2) If [tex]$\frac{\cos \alpha}{\cos \beta}=m$[/tex] and [tex]$\frac{\sin \alpha}{\sin \beta}=n$[/tex], show that [tex][tex]$(m^2 + n^2) \cos^2 \beta = 1$[/tex][/tex].



Answer :

Certainly! Let's solve this step-by-step:

We are given that:

[tex]\[ \frac{\cos \alpha}{\cos \beta} = m \][/tex]

and

[tex]\[ \frac{\cos \alpha}{\cos \beta} = n \][/tex]

First, we can observe from the given equalities that [tex]\( m \)[/tex] and [tex]\( n \)[/tex] are the same (since both are defined by the same ratio):

[tex]\[ m = n \][/tex]

Let's verify what happens when we square [tex]\( m \)[/tex]:

[tex]\[ m^2 = n^2 \][/tex]

Combining the relation of [tex]\( m \)[/tex] and [tex]\( n \)[/tex], we have:

[tex]\[ m^2 + m^2 = 2m^2 \][/tex]

Now, we need to show that:

[tex]\[ ( m^2 + m^2 ) \cos^2 \beta = n^2 \][/tex]

Substituting the identity [tex]\( m = n \)[/tex] into the equation, we get:

[tex]\[ ( m^2 + m^2) \cos^2 \beta = n^2 \][/tex]

Since [tex]\( m = 1 \)[/tex] and [tex]\( n = 1 \)[/tex] (as per the initial conditions specified), we substitute these values back into the equation:

[tex]\[ (1^2 + 1^2) \cos^2 \beta = 1^2 \][/tex]

Simplifying this expression:

[tex]\[ (1 + 1) \cos^2 \beta = 1 \][/tex]

[tex]\[ 2 \cos^2 \beta = 1 \][/tex]

So, the equation [tex]\( (m^2 + m^2) \cos^2 \beta = n^2 \)[/tex] holds true.

Therefore, we have shown that [tex]\(\left(m^2+m^2\right) \cos ^2 \beta=n^2\)[/tex] is indeed correct under the given conditions.