Answer:
C
Explanation:
Given
tanθ =
=
This is a right triangle with legs 1 and 2
Using Pythagoras' identity
hypotenuse² = 1² + 2² = 1 + 4 = 5 ( take square root of both sides )
hypotenuse =

θ is in the 3rd quadrant where sinθ < 0 , then
sinθ =
= -
← rationalise the denominator
= -
×

= -
→ C