$${{{e^{i\phi }}\, - \,{e^{ - i\phi }}} \over 2}$$

$${{{e^{i\phi }}\, - \,{e^{ - i\phi }}} \over {2i}}$$

$${{{e^{i\phi }}\, + \,{e^{ - i\phi }}} \over i}$$

$${{{e^{i\phi }}\, + \,{e^{ - i\phi }}} \over 2}$$