5.3 Sum and
Difference Identities for Cosine
Common ERROR!!
and similarly for sum and sum or difference with sine!!
Cosine of a Sum or Difference
Fraction review:!!
Common
Sums and Differences
Note:
Find values of sums and
differences of multiples of 30/45/60
etc.
Example
1
Find the
exact value of each expression:
a) 
b) 
c) 
Co function Identities
Similar
identities exist for 
Example
Find and
angle θ that satisfies each of the following:
a) 
b)
c) 
Using Formulas to find a function of
a Single Variable
Example
Write 
as a trigonometric
function of θ alone.
Finding
cosine of a sum given information about the addends
Example
Suppose
that 
and both s and t are in quadrant IV.
Find 
Ans: 