Polar coordinates of mathematical problems! What is the distance between the centers of two circles with polar coordinate equations ρ = cos θ and ρ = sin θ?

Polar coordinates of mathematical problems! What is the distance between the centers of two circles with polar coordinate equations ρ = cos θ and ρ = sin θ?

If ρ = cos θ is replaced by the general equation, it is x ^ 2 + y ^ 2 = y, and the center of the circle is (0,1 / 2)
If ρ = sin θ is replaced by the general equation, it is x ^ 2 + y ^ 2 = x, and the center of the circle is (1 / 2,0)
The distance d between the centers of two circles is 2 / 2 of the root sign

On the singular and plural of nouns
Dogs are our companions
dog/dogs?
The flowers are beautiful
flower/flowers?
Apples are delicious
apple/apples?
Is the subject a general term?
Is the subject of a sentence singular or plural

Plural

How many nouns have the same singular and plural

The singular and plural of the following nouns are in the same form:
Fish, deer, sheep, works, means, Swiss, Swiss, Chinese
Plural nouns only
Trousers pants, pants pants, shorts pants
Glasses, compasses, compasses, scales, pliers, clips, scissors
There are three types of plural of "a Chinese"
(1) The singular and plural of Chinese, Japanese and Swiss are in the same form, without s;
(2) In English, French and Dutchman, the plural number should change man into men;
(3) In other countries, people who end with - an and - Ian directly add S. for example, Americans, Australians, Indians and so on