Answer:
8.4 (rounded to 1 dp)
Step-by-step explanation:
1) Identify the number of angles and sides given if you cannot use Pythagoras or SohCahToa.
2) You have 2 angles and 1 side, so you know you must use sine rule: a over sinA = b over sinB
a = side length, sin(A) = angle opposite side
b = side length, sin(B) = angle opposite side
3) This means:
13/sin(90) = x/sin(40)
4) rearrange for x:
x = 13/sin(90) * sin(40)
= 8.356...
5) Round to however many sig figs/dps they're asking for
Example: 1 dp
AB = 8.4
3 sig figs
AB = 8.36
