Why was the pyramids built big?

According to my notes, pyramids were built for 2 things.
1. Burial place for tombs
2. To show the pharaoh's power.

Sorry I made a mistake my friend told me that.

Ok so I look it up
they used it for tombs and also I found more facts on it
The shape of Egyptian pyramids is thought to represent the primordial mound from which the Egyptians believed the earth was created. The shape of a pyramid is thought to be representative of the descending rays of the sun, and most pyramids were faced with polished, highly reflective white limestone, in order to give them a brilliant appearance when viewed from a distance. Pyramids were often also named in ways that referred to solar luminescence. For example, the formal name of the Bent Pyramid at Dahshur The Southern Shining Pyramid, and that of Senwosret at el-Lahun was Senwosret is Shining.