Question

show that cos a + cos b + cos y + cos(a + b + y) = 4 cos(a+b/2).cos(b+y/2).cos(y+a/2)
​

Answer 1

Answer:

cos a + cos b + cos c + cos (a+b+c)

=2 cos ((a+b)/2) cos ((a-b)/2) + 2 cos ((c+a+b+c)/2) cos ((c-a-b+c)/2)

= 2cos((a+b)/2)cos((a-b)/2) + 2cos((a+b+2c)/2)cos((-a-b)/2)

= 2cos((a+b)/2)cos((a-b)/2) + 2cos((a+b+2c)/2)cos((-(a+b))/2)

Remember cos(-x) = cos x and cos a + cos b is 2cos((a+b)/2)

= 2cos((a+b)/2)cos((a-b)/2) + 2cos((a+b+2c)/2)cos((a+b)/2)

2cos((a+b)/2) is taken common

= 2 cos ((a+b)/2) { cos ((a-b)/2) + cos ((a+b+2c)/2) }

= 2 cos ((a+b)/2) { 2cos((a-b+a+b+2c)/2*2) cos(a-b-a-b-2c)/2*2) }

= 2 cos ((a+b)/2) { 2 cos ((2a+2c)/4) cos((-2b-2c)/4) }

= 4 cos ((a+b)/2) cos ((a+c)/2) cos ((b+c)/2)

Step-by-step explanation:

mark me as branliest

Answer 2

Step-by-step explanation:

Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state.