Answer:
the third option is the correct
The double angle identities are


Then


The second identity together with the Pythagorean identity,
, gives us another equivalent expression:

so

So to figure out 10% of this would be to remove the 0. that would be six. since 30÷10 is 3, we have to do 6×3. that would be 18, so 30% of 60 is 18