1 kg=1000g*1000mg/1g=1000000mg =10⁶ mg
or you can use proportion
1000g - x mg
1 g -1000mg
x=1000*1000=1000000mg
1kg=10⁶ mg
This one is a bit more complicated but i believe the answer is -1/4
Answer:

If we multiply by cross we got:

We can divide both sides of the last equation by
and we got:

And if we apply arcsin in both sides we got:

And the best solution would be:
C) pi/2
Step-by-step explanation:
For this case we want to solve the following equation:

And we know that by definition 
And replacing we got:

If we multiply by cross we got:

We can divide both sides of the last equation by
and we got:

And if we apply arcsin in both sides we got:

And the best solution would be:
C) pi/2