UML use case extend relationship is used to show how and when some optional extending use case can be inserted into extended (base) use case.

UML use case extend relationship is used to show how and when some optional extending use case can be inserted into extended (base) use case. For example, Registration use case could be extended with optional Get Help On Registration use case.

requirements - Are using <> and <> relationship

Use Case Diagram (available in CORE Spectrum)

10 Use Case Diagram Examples (and How to Create Them) - Venngage

What is the difference between extend and include functions in a

Dependencies - Learning UML [Book]

Concept: Use-Case Model

Use Case Diagrams

Use Case Diagram Tutorial (Guide with Examples) – Creately Help Center

System Design — UML Use Case Diagram, by JIN