## Trigonometry 7th Edition

$(90- x)^{\circ}$ $\sin x^{\circ} = \cos ( 90- x)^{\circ}$
$\sin x^{\circ} = \cos ( 90- x)^{\circ}$ Reason- sine and cosine are cofunctions and $x^{\circ} + (90-x)^{\circ} = 90^{\circ}$ i.e. $x^{\circ}$ and $(90-x)^{\circ}$ are complementary angles.