Question

(iii) cos (a + B) sin ß + cos (a - Y) sin y = sin (a +B). cos B-sin (a - Y) cos y.
​

Answer 1

Answer:

Step-by-step explanation:f cosx+cosy+cosα=0……(i)

sinx+siny+sinα=0……(ii)

then  cot(  

2

x+y

​  

)=?

Now,

cosx+cosy=−cosα

2cos(  

2

x+y

​  

).cos(  

2

x−y

​  

)=−cosα……(iii)

sinx+siny=−sinα

2sin(  

2

x+y

​  

).cos(  

2

x−y

​  

)=−sinα……(iv)

By (iii)÷(iv)

2×sin(  

2

x+y

​  

).cos(  

2

x−y

​  

)

2×cos(  

2

x+y

​  

).cos(  

2

x−y

​  

)

​  

=  

−sinα

−cosα

​  

 

⇒cot(  

2

x+y

​  

)=cotα