This CK12 Pythagorean Theorem flexbook is a great resource for students: https://goopenva.org/courses/the-pythagorean-formula-mini-flexbook/view

I would also consider using this proof of the Pythagorean Theorem Desmos Activity https://teacher.desmos.com/activitybuilder/custom/5688b71ef489315635d23769 from Ballif, Serge as a way to help students develop an understanding of why the Pythagorean Theorem works.

The Schoolyard Problem from the VDOE Mathematics Instructional Plans is a great addition to your lesson where students can apply their critical thinking skills to an application problem. http://www.doe.virginia.gov/testing/sol/standards_docs/mathematics/2016/mip/geo/mip-G-8a-pythag-relationship.docx