The point (2,-4) is on the terminal side of an angle t. Find sin( t ) to 2 decimal places

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sin t = y/r

r = √[ x^2 + y^2 ]  = √[ (2)^2 + (-4)^2 ]  =  √20  =   2√5

sin t  =  -4/ [2√5]  =  -2 / √5  ≈   -0.89

And to find t, we have

arcsin ( -2 / √5 )  = t  = -63.43°  =  296.57°  .....since (2,-4)  occurs in the 4th quadrant