Question

Please help me with question 2

Answer 1

sin(-a)= -15 /17

Explanation:

Alright, lets remember that sin(x) is odd function, which means that

wherever you watch an expression like this: sin(-a), you can use the odd functions property, and turn it like the following

sin(-a)= - sin(a)

Now, other thing to remember:
`(sin(x))^(2)+(cos(x))^(2)=1`

So, we can obtain any value for sin(x) function starting from the opposite function, cos(x), using the following:

`sin(x)=\sqrt{1-(cos(x))^(2) }`

So, if cos(a)= - 8 / 17, using the above equation we obtain the value for sin(a)

`sin(a)=\sqrt{1 - (cos(a))^(2) } = \sqrt{1 - ( (8)/(17) )^(2)  }= \sqrt{(225)/(289) }  =15/17`

Using the odd function property, we get the following result

sin(-a)= - sin(a) = -15/17