Today's geometry lesson: How to shoot Barack Obama, by the teacher questioned by the Secret Service

A teacher who used the hypothetical assassination of President Barack Obama to help his students understand geometry has been questioned by the U.S. Secret Service.
Maths teacher Gregory Harrison used the mock killing of Mr Obama so his students could better understand how to use angles, officials said.
Students in his class at Corner High School in Birmingham, Alabama, said Mr Harrison used the example of where an assassin would stand to get the best shot at killing the president.

A teacher who used the mock killing of Barack Obama so his students understood angles has been questioned by the U.S. Secret Service
He pointed out the best angles a shooter would use to hit the target and explained the use of parallel lines, they said.
Joseph Brown, who was in Mr Harrison's geometry class, said: 'He was talking about angles and said, "If you're in this building, you would need to take this angle to shoot the president."'
The Secret Service interviewed Mr Harrison after being alerted to the unusual teaching methods but has decided not to file charges.
Spokesman Roy Sexton said: 'We did not find a credible threat.'
Superintendent Phil Hammonds said the teacher has been placed on paid leave.
'We are going to have a long conversation with him about what's appropriate,' he said.
'It was extremely poor judgment on his part, and a poor choice of words.'
Mr Obama receives almost four times as many death threats as any other U.S. president.