Could you help me with following trigonometric identity proofs question Verify Sin^2 u/2 = ( Sin^2 u + cos u - 1 ) Divided by ( 2 cos u )

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?

An electrician cuts a 136 foot long piece of cable. one piece is 16 feet less than 3 times the length of the other piece. find the length of each piece

Mr. roseanne will buy 12 1/2 pounds beef for for a cookout. the price for the first 3 pounds of beef is $4.99 per pound. after that, the price is $4.49 per pound. how much will mr. roshan pay for the beef