Question

if sinα + sinβ = a and cosα + cosβ = b then show that cos(α+β)=(b²-a²)/(b² + a²)

Answer 1

The area, originally inhabited by the Tongva (or Gabrielino) Indians (its name derives from the Indian word kukamonga, meaning “sandy place”), was explored in 1769 by a Spanish expedition led by Gaspar de Portolá. ...