Final: Two Angles
Part of the Trig Identities section of Coddy's Trigonometry journey. Lesson 47 of 52.
Prove the identity in the prompt. Two different angles appear, x and y.
Challenge
Prove that (cos(x + y) + sin(x)sin(y))/cos(x) equals cos(y): rewrite it until the board reads cos(y). Then press Check.
Try it yourself
(cos(x + y) + sin(x)sin(y))/cos(x)
Simplify the expression
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Trig Identities
1Identities on the Circle
sin²x + cos²x = 1Squares Erase the SignsIdentity or Equation?Recap: the Circle Identity4Even, Odd and Cofunctions
Negative AnglesEven and Odd in a ProofEven and Odd GraphsCofunctionsRecap: Signs of Angles7Double-Angle Formulas
sin 2x = 2 sin x cos xThree Forms of cos 2xExact Values, DoubledSquare, Then DoubleThe Graph of 2 sin x cos xRecap: Double Angles10Final Challenges
Final: Two AnglesFinal: Tangents to sin 2xFinal: An Exact ProductFinal: A Wave in DisguiseFinal: Two SquaresFinal: Choose the Form2Reciprocal and Quotient
The Quotient IdentitySecant, Cosecant, CotangentDividing by a FractionWhere They BreakRecap: Reciprocals5Proving Identities
Work on One SideRewrite in sin and cosFactor FirstMake One FractionProofs That Go WrongRecap: Prove It8Half Angles, Power Reduction
Power Reductionsin²x Is a WaveHalf-Angle Valuestan of a Half AngleRecap: Half Angles