Question

Find the simplified, exact value of each expression.
cos(-30)
sin(-pi/2)
sin(-13pi/6)

Answer 1

negative angle identities
\[\rm \sin(-x) = -\sin(x) ~~~\color{red}{odd}\]\[\rm \cos(-x)= \cos(x)~~~~~\color{red}{even}\]\[\rm Tan(-x)=-\tan(x)~~\color{red}{odd}\]

Answer 2

and then you can use unit circle to find EXACT value of each ratio
or 30-60-90 theorem

Answer 3

for the last one
first you should apply the negative identity rules
and then subtract 2pi( 2pi is one complete circle )
so subtract 2pi from 13pi/2
simplify and then use the unit circle to find EXACT value