[tex]y = \frac{ \cos60 {}^{0} + \cos270 {}^{.} }{ \cos0 + \cos90 {}^{0} \times \cos180 {}^{.} } \\ [/tex]
[tex]y = \frac{ \frac{1}{2} + 0 }{1 + 0 \times ( - 1)} \\ [/tex]
[tex]y = \frac{ \frac{1}{2} }{1 + 0} \\ [/tex]
[tex]y = \frac{ \frac{1}{2} }{1} \\ [/tex]
[tex]y = \frac{1}{2} \\ [/tex]
