Sum and Difference Identities - Pretty Math

1 Quotient Identities sintancos coscotsin Reciprocal Identities 1cscsin 1seccos 1cottan Pythagorean Identities 22sincos1 22tan1 sec 221 cotcsc Even and Odd Identities Sum and Difference Identities cos() cos cossin sin cos() cos cossin sin sin() sin coscos sin sin() sin coscos sin Double-Angle and Half-Angle Identities sin 22sin cos 22cos 2cossin 2cos 21 2sin sinsincoscostantan csccscsecseccotcot 1 cossin221 coscos221 costan21 cos tantantan1 tan tan tantantan1 tan tan 1 cossintan2sin1 cos 2cos 22 cos1 22 tantan 21 tan Write your questions here!

2 Sum and Difference Identities Is it true? sin 45 30 sin45 sin30 Ex 1: Ex 2: Ex 3: NOTESNow, summarize your notes here! Ex 4: Write the expression as the sine, cosine, or tangent of an angle. Ex 5: Find sin (x - y) given the following: Ex 6: Is the equation an identity? SUMMARY: Sum and Difference Identities Directions: Tell whether each statement is true or false. 1) sin75 sin50cos25 cos25sin25 2) cos15 cos60cos45 sin60sin45 3) tan225 tan180 tan451 tan180tan45 Directions: Write the expression as the sine, cosine or tangent of an angle. 4) sin42cos17 cos42sin17 5) 6) cos cos sin sin Directions: Use the sum or Difference identity to find the exact value.

3 7) tan195 8) cos255 9) sin165 10) cos PRACTICE11) sin 12) tan Directions: Find the exact value. 13) sin Given: cos 0 , tan 0 , 14) tan Given: cosx 90 0 , cos 180 90 , 15) sin Given: sin , cos , 16) cos Given: cos , 2 tan , Directions: Is the equation an identity?

4 Explain using the sum or Difference Identities 17) cos cos 18) sin sin REVIEW SKILLZ: Directions: Solve each triangle. 1) 2) Application and Extension 1) Find the exact value. 2) Find the exact value. cos285 cos Given: cos , 2 tan , 3) Verify the following DOUBLE ANGLE Identities .

5 ( (2x) = sin (x + x) a) sin 2 2sin cos b) cos 2 2 1 5) When a wave travels through a taut string (like guitar string), the displacement y of each point on the string depends on the time t and the point s position x. The equation of a standing wave can be obtained by adding the displacements of two waves traveling in opposite directions. Suppose two waves can be modeled by the following equations: cos cos Find 6) Mr. Sullivan has been carrying the other Algebros on his back for the last several years. He knows from Mr. Rahn s physics class that the force F (in pounds) on a person s back when he bends over at an angle is.

6 Simplify the above formula. PC Practice 28-7:17 AMPC Practice 28-7:18 AMPC Practice 28-7:18 AMYou must complete this before retaking the MC again. Remember it is all about LEARNING so take your time and learn how to do these skills. If you need help please ask! NAME:_____ Corrective Assignment Directions: Write the expression as the sine, cosine or tangent of an angle. 1) sin27cos24 cos27sin24 2) 3) cos cos sin sin Directions: Use the sum or Difference identity to find the exact value. 4) cos255 5) sin 105 6) sin 7) tan Directions: Find the exact value.

7 8) tan Given: cos 0 , tan 0 , 9) sin Given: cosx 90 0 , cos 180 90 , 10) cos Given: sin , tan , 11) sin Given: cos , 2 tan , ANSWERS TO CORRECTIVE ASSIGNMENT: Make sure you check all your answers and make sure you KNOW how to do all of them. You could simply copy answers but that s not the point. The point is that you have to learn how to do this so please make sure that for any you don t understand you get help BEFORE taking the Mastery Check again.

8 1) sin3 2) tan37 3) cos 4) 5) 6) 7) 3 2 8) 9) 45 10) 1665 11) 3685 Practice with Sum and Difference Identities Write each expression as the sine, cosine, or tangent of a single angle. _____ 1. cos80 cos20 +sin80 sin20 _____ 2. sin30 cos45 +cos30 sin45 _____ 3. cos20 cos45 sin20 sin45 _____ 4. tan90 tan10 1+tan90 tan10 _____ 5. sin25 cos20 cos25 sin20 _____ 6. tan120 +tan45 1 tan120 tan45 _____ 7. sin 4cos 3 cos 4sin 3 _____ 8. cos 2cos2 3+sin 2sin2 3 _____ 9. tan 9 tan 41+tan 9tan 4 _____ 10. sin105 cos85 cos105 sin85 _____ 11. cos45 cos60 +sin45 sin60 _____ 12. cos45 cos60 sin45 sin60 Write each expression as a sine, cosine, or tangent of a sum or Difference of special value angles.

9 _____ 13. sin105 _____ 14. cos 12 _____ 15. tan7 12 _____ 16. cos( 75 ) _____ 17. sin165 _____ 18. cos195 _____ 19. tan285 _____ 20. sin13 12 Determine if each equation is true or false. If the statement is false, highlight the incorrect section. _____ 21. cos57 =cos(40 +17 ) _____ 22. sin75 =sin50 cos25 cos50 sin25 _____ 23. tan45 =tan40 +tan5 1+tan40 tan5 _____ 24. sin40 =sin50 sin10 _____ 25. cos65 =cos35 cos30 +sin35 sin30 _____ 26. sin105 =sin90 cos15 +sin15 cos90 _____ 27. tan75 =tan90 tan15 1+tan15 tan90 _____ 28. tan75 =tan80 tan5 1+tan70 tan5 _____ 29. cos60 =cos20 +cos40 _____ 30. sin25 =sin10 cos15 +sin10 cos15 Practice with Sum and Difference Identities KEY Write each expression as the sine, cosine, or tangent of a single angle.

10 _____ 1. cos80 cos20 +sin80 sin20 _____ 2. sin30 cos45 +cos30 sin45 _____ 3. cos20 cos45 sin20 sin45 _____ 4. tan90 tan10 1+tan90 tan10 _____ 5. sin25 cos20 cos25 sin20 _____ 6. tan120 +tan45 1 tan120 tan45 _____ 7. sin 4cos 3 cos 4sin 3 _____ 8. cos 2cos2 3+sin 2sin2 3 _____ 9. tan 4 tan 91+tan 4tan 9 _____ 10. sin105 cos85 cos105 sin85 _____ 11. cos45 cos60 +sin45 sin60 _____ 12. cos45 cos60 sin45 sin60 Write each expression as a sine, cosine, or tangent of a sum or Difference of special value angles. _____ 13. sin105 _____ 14. cos 12 _____ 15. tan7 12 _____ 16. cos( 75 ) _____ 17. sin165 cos60 sin75 cos65 tan80 sin5 tan165 sin( 12) cos( 6) tan5 36 sin20 cos( 15 ) cos105 sin(60 +45 ) cos( 3 4) tan( 3+ 4) cos(45 120 ) sin(120 +45 ) _____ 18.