The 'upside down' triangle symbol is the (greek?) letter Nabla. Nabla means the gradient. The gradient is the vector field whoose components are the partial derivatives of a function F given by (df/dx, df/dy).
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No one, not the place to ask btw.
The adjective form of who is spelled whose. The spelling of the contraction is who's meaning "who is."
TCS TCS
DAISY! Ambre looks very old!
Black hole
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She liked the name harry and the potters were a family who lived in her street so she "borrowed" the name.
Montana
Simon, whoose name was later changed by Christ to Peter, and his brother Andrew were fishermen on the Sea of Galilee