Practice: pg 440 #1-6, 8-13, read and select from pg 441
Trigonometric Identities and Equations: Unit Summary
Things to know...
1. Memorize the 18 key identities/formulas.
2. Memorize the two special triangles.
3. Be able to relate to trigonometric functions in the context of a

transformation; ie... cos   sin    .

2
4. The cosine function is even --> cos(  )  cos( )
5. The sine and tan function are odd --> sin(  )   sin(  ) , tan(  )   tan( )
6. The sin, cos, tan of any angles is equal to the sin, cos, tan of the
related angle (a negative should be placed in front depending on the
quadrant).
7. Be able to use compound angle formulas to determine exact values of
trig functions for angles not found in the special triangles... 150, 750, ...
8. Use the graphs of sine, cosine, tangent to determine angles or ratios.
For example sin(900) = 1 as seen on the graph for y = sinθ.
9. Be able to derive and apply the double angle formulas.
10.Prove identities using known identities from your formula sheet.
11.Be familiar with some key strategies to prove identities. Some
strategies include...
 csc, sec, and cot can be turned into sin, cos, tan.
sin 
.
cos 
 being able to go back and forth from sin 2  to cos 2  .
 all instances of tan can be turned into
 some known identities are difference of squares ...
sin 2   1  cos 2  can be changed to (1  cos  )(1  cos  ) .
 the conjugate can be used to complete diff. of squares; this can
help turn an unwanted sine into a cosine or vice versa.
 cos(2θ) has three forms... choose wisely when changing it.
12. Be able to solve trigonometric equations by isolating the basic trig
function first.
13.Solve quadratic trigonometric functions...
 all elements in the equation have to use the same trig function;
the squared parts are easiest to change if necessary.
 equations can sometimes be solved by factoring and using the
zero principle.