Are there answer choices ?
The answer will be 4.9. =)
Since we know 1 metre is 0.01 dekametres, we can use this to answer the question!
We simply multiply 490 by 0.01. =)
Answer:
Using Pythagoras Theorem, squareroot 15^2 - 5^2.
After you found the opposite length, use the cosine rule to find angle x.