A 15 foot ladder is leaning against a house such that the bottom of the ladder is 4 feet from the house. What is its angle of elevation

Ithink it’s true as the answer.

It is the doctrine that the us had the right and duty to expand throughout north america. it just means they believed they had the right to expand westward and they did! they stated with the 13 colonies and then they kept moving gaining different territories throughout the years