Which of the following sentences are statement ? Justify
(i) A triangle has three sides.
(ii) 0 is a complex number.
(ii) Sky is red.
(iv) Every set is an infinite set.
(v) `15 + 8 gt 23`.
(vi) y + 9 =7
(vii) Where is your bag?
(viii) Every square is a rectangle.
(ix) Surn of opposite angles of a cyclic quadrilateral is `180^(@)`.
(x) ` sin ^(2) x + cos^(2)x =0`

Explanation

To determine which of the given sentences are statements, we need to recall that a statement is a declarative sentence that is either true or false, but not both. Questions, commands, or expressions of opinion are not considered statements. Let's analyze each sentence step by step:

1. **Sentence (i): A triangle has three sides.**
- This is a declarative sentence that is true.
- **Conclusion:** It is a statement.

2. **Sentence (ii): 0 is a complex number.**
- This is a declarative sentence that is true, as 0 can be expressed in the form of a complex number (0 + 0i).
- **Conclusion:** It is a statement.

3. **Sentence (iii): Sky is red.**
- This is a declarative sentence that can be false (the sky is not always red).
- **Conclusion:** It is a statement (even though it is false).

4. **Sentence (iv): Every set is an infinite set.**
- This is a declarative sentence that is false, as there are finite sets (e.g., {1, 2, 3}).
- **Conclusion:** It is a statement (even though it is false).

5. **Sentence (v): 15 + 8 > 23.**
- This is a declarative sentence that is false, since 15 + 8 equals 23, not greater than 23.
- **Conclusion:** It is a statement (even though it is false).

6. **Sentence (vi): y + 9 = 7.**
- This is an equation, not a declarative sentence. It does not assert a truth value.
- **Conclusion:** It is not a statement.

7. **Sentence (vii): Where is your bag?**
- This is a question and does not assert a truth value.
- **Conclusion:** It is not a statement.

8. **Sentence (viii): Every square is a rectangle.**
- This is a declarative sentence that is true.
- **Conclusion:** It is a statement.

9. **Sentence (ix): Sum of opposite angles of a cyclic quadrilateral is 180°.**
- This is a declarative sentence that is true.
- **Conclusion:** It is a statement.

10. **Sentence (x): sin²x + cos²x = 0.**
- This is a declarative sentence that is false, as the correct identity is sin²x + cos²x = 1.
- **Conclusion:** It is a statement (even though it is false).

### Summary of Statements:
- Statements: (i), (ii), (iii), (iv), (v), (viii), (ix), (x)
- Not Statements: (vi), (vii)