These are as follows:
1.informative
2. explainatory
3. conclusive ...

Introduction:
A formal letter is a type of communication that is used for official purposes. It is written in a professional tone and follows a specific format. A formal letter is used for various reasons, such as making a complaint, requesting information or action, or expressing gratitude. In this article, we will discuss how to write a formal letter in three paragraphs.

Paragraph 1: The Opening
The opening paragraph of a formal letter should include the following:
- The purpose of the letter
- The recipient's name and address
- The date
- A formal greeting

The purpose of the letter should be clearly stated in the opening paragraph. This will help the recipient understand the reason for the letter and what they need to do in response. The recipient's name and address should be included to ensure that the letter reaches the correct person. The date is important as it provides a reference for future communication. A formal greeting, such as "Dear Sir/Madam" or "To Whom It May Concern" should be used.

Paragraph 2: The Body
The body of the letter should provide details about the purpose of the letter. This may include information about a problem, a request for information or action, or an expression of gratitude. The body should be clear and concise, and the information should be presented logically. It is important to provide any relevant background information to help the recipient understand the situation. If the letter is a complaint, it is important to be polite but firm. If the letter is a request, it is important to be clear about what is being asked for.

Paragraph 3: The Closing
The closing paragraph of a formal letter should include the following:
- A summary of the purpose of the letter
- A polite request for action or response
- A formal closing

The summary of the purpose of the letter should be brief and to the point. This will help the recipient remember the key points of the letter. A polite request for action or response should be included to encourage the recipient to take the necessary steps. A formal closing, such as "Yours faithfully" or "Sincerely" should be used. The letter should be signed and the writer's name should be printed below the signature.