Prove that.....

Question

Anyone help me solve this?

Prove that:

cos(y-Π)+sin(y+Π/2)=0

 

 

Answer 1

You can use the sum and difference formulas for sin and cos:

 

cos (y - Π) = cos y * cos Π + sin y * sin Π = cos y * (-1) + sin y * 0 = - cos y

 

sin (y+Π/2) = sin y cos Π/2 + cos y sin Π/2 = sin y * 0 + cos y * 1 = cos y

 

So add the two together and you get -cos y + cos y = 0