Question

Express `cos(pi/2+x-y)` in terms of trigonometric ratios of `x` and `y`?

Answer 1

Please see beloww.

Explanation:

As `cos(pi/2+A)=-sinA` and

`sin(x-y)=sinxcosy-cosxsiny`

`cos(pi/2+x-y)=-sin(x-y)`

= `-(sinxcosy-cosxsiny)`

= `cosxsiny-sinxcosy`