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Popular Trigonometry >

cos((5pi)/4+x)+sin((5pi)/4-x)=0

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Solution

cos(45π​+x)+sin(45π​−x)=0

Solution

x=4π​+πn
+1
Degrees
x=45∘+180∘n
Solution steps
cos(45π​+x)+sin(45π​−x)=0
Rewrite using trig identities
cos(45π​+x)+sin(45π​−x)=0
Rewrite using trig identities
sin(45π​−x)
Use the Angle Difference identity: sin(s−t)=sin(s)cos(t)−cos(s)sin(t)=sin(45π​)cos(x)−cos(45π​)sin(x)
Simplify sin(45π​)cos(x)−cos(45π​)sin(x):22​(−cos(x)+sin(x))​
sin(45π​)cos(x)−cos(45π​)sin(x)
sin(45π​)cos(x)=−22​cos(x)​
sin(45π​)cos(x)
sin(45π​)=−22​​
sin(45π​)
Rewrite using trig identities:sin(π)cos(4π​)+cos(π)sin(4π​)
sin(45π​)
Write sin(45π​)as sin(π+4π​)=sin(π+4π​)
Use the Angle Sum identity: sin(s+t)=sin(s)cos(t)+cos(s)sin(t)=sin(π)cos(4π​)+cos(π)sin(4π​)
=sin(π)cos(4π​)+cos(π)sin(4π​)
Use the following trivial identity:sin(π)=0
sin(π)
sin(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​sin(x)021​22​​23​​123​​22​​21​​xπ67π​45π​34π​23π​35π​47π​611π​​sin(x)0−21​−22​​−23​​−1−23​​−22​​−21​​​
=0
Use the following trivial identity:cos(4π​)=22​​
cos(4π​)
cos(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​cos(x)123​​22​​21​0−21​−22​​−23​​​xπ67π​45π​34π​23π​35π​47π​611π​​cos(x)−1−23​​−22​​−21​021​22​​23​​​​
=22​​
Use the following trivial identity:cos(π)=(−1)
cos(π)
cos(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​cos(x)123​​22​​21​0−21​−22​​−23​​​xπ67π​45π​34π​23π​35π​47π​611π​​cos(x)−1−23​​−22​​−21​021​22​​23​​​​
=(−1)
Use the following trivial identity:sin(4π​)=22​​
sin(4π​)
sin(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​sin(x)021​22​​23​​123​​22​​21​​xπ67π​45π​34π​23π​35π​47π​611π​​sin(x)0−21​−22​​−23​​−1−23​​−22​​−21​​​
=22​​
=0⋅22​​+(−1)22​​
Simplify=−22​​
=−22​​cos(x)
Multiply fractions: a⋅cb​=ca⋅b​=−22​cos(x)​
=−22​cos(x)​−cos(45π​)sin(x)
cos(45π​)sin(x)=−22​sin(x)​
cos(45π​)sin(x)
cos(45π​)=−22​​
cos(45π​)
Rewrite using trig identities:cos(π)cos(4π​)−sin(π)sin(4π​)
cos(45π​)
Write cos(45π​)as cos(π+4π​)=cos(π+4π​)
Use the Angle Sum identity: cos(s+t)=cos(s)cos(t)−sin(s)sin(t)=cos(π)cos(4π​)−sin(π)sin(4π​)
=cos(π)cos(4π​)−sin(π)sin(4π​)
Use the following trivial identity:cos(π)=(−1)
cos(π)
cos(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​cos(x)123​​22​​21​0−21​−22​​−23​​​xπ67π​45π​34π​23π​35π​47π​611π​​cos(x)−1−23​​−22​​−21​021​22​​23​​​​
=(−1)
Use the following trivial identity:cos(4π​)=22​​
cos(4π​)
cos(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​cos(x)123​​22​​21​0−21​−22​​−23​​​xπ67π​45π​34π​23π​35π​47π​611π​​cos(x)−1−23​​−22​​−21​021​22​​23​​​​
=22​​
Use the following trivial identity:sin(π)=0
sin(π)
sin(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​sin(x)021​22​​23​​123​​22​​21​​xπ67π​45π​34π​23π​35π​47π​611π​​sin(x)0−21​−22​​−23​​−1−23​​−22​​−21​​​
=0
Use the following trivial identity:sin(4π​)=22​​
sin(4π​)
sin(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​sin(x)021​22​​23​​123​​22​​21​​xπ67π​45π​34π​23π​35π​47π​611π​​sin(x)0−21​−22​​−23​​−1−23​​−22​​−21​​​
=22​​
=(−1)22​​−0⋅22​​
Simplify=−22​​
=−22​​sin(x)
Multiply fractions: a⋅cb​=ca⋅b​=−22​sin(x)​
=−22​cos(x)​−(−22​sin(x)​)
Apply rule −(−a)=a=−22​cos(x)​+22​sin(x)​
Since the denominators are equal, combine the fractions: ca​±cb​=ca±b​=2−2​cos(x)+2​sin(x)​
Factor out common term 2​=22​(−cos(x)+sin(x))​
Cancel 22​(−cos(x)+sin(x))​:2​−cos(x)+sin(x)​
22​(−cos(x)+sin(x))​
Apply radical rule: 2​=221​=2221​(sin(x)−cos(x))​
Apply exponent rule: xbxa​=xb−a1​21221​​=21−21​1​=21−21​−cos(x)+sin(x)​
Subtract the numbers: 1−21​=21​=221​−cos(x)+sin(x)​
Apply radical rule: 221​=2​=2​−cos(x)+sin(x)​
=2​−cos(x)+sin(x)​
Rationalize 2​−cos(x)+sin(x)​:22​(sin(x)−cos(x))​
2​−cos(x)+sin(x)​
Multiply by the conjugate 2​2​​=2​2​(−cos(x)+sin(x))2​​
2​2​=2
2​2​
Apply radical rule: a​a​=a2​2​=2=2
=22​(−cos(x)+sin(x))​
=22​(sin(x)−cos(x))​
=22​(−cos(x)+sin(x))​
Use the Angle Sum identity: cos(s+t)=cos(s)cos(t)−sin(s)sin(t)=cos(45π​)cos(x)−sin(45π​)sin(x)
Simplify cos(45π​)cos(x)−sin(45π​)sin(x):22​(−cos(x)+sin(x))​
cos(45π​)cos(x)−sin(45π​)sin(x)
cos(45π​)cos(x)=−22​cos(x)​
cos(45π​)cos(x)
cos(45π​)=−22​​
cos(45π​)
Rewrite using trig identities:cos(π)cos(4π​)−sin(π)sin(4π​)
cos(45π​)
Write cos(45π​)as cos(π+4π​)=cos(π+4π​)
Use the Angle Sum identity: cos(s+t)=cos(s)cos(t)−sin(s)sin(t)=cos(π)cos(4π​)−sin(π)sin(4π​)
=cos(π)cos(4π​)−sin(π)sin(4π​)
Use the following trivial identity:cos(π)=(−1)
cos(π)
cos(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​cos(x)123​​22​​21​0−21​−22​​−23​​​xπ67π​45π​34π​23π​35π​47π​611π​​cos(x)−1−23​​−22​​−21​021​22​​23​​​​
=(−1)
Use the following trivial identity:cos(4π​)=22​​
cos(4π​)
cos(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​cos(x)123​​22​​21​0−21​−22​​−23​​​xπ67π​45π​34π​23π​35π​47π​611π​​cos(x)−1−23​​−22​​−21​021​22​​23​​​​
=22​​
Use the following trivial identity:sin(π)=0
sin(π)
sin(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​sin(x)021​22​​23​​123​​22​​21​​xπ67π​45π​34π​23π​35π​47π​611π​​sin(x)0−21​−22​​−23​​−1−23​​−22​​−21​​​
=0
Use the following trivial identity:sin(4π​)=22​​
sin(4π​)
sin(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​sin(x)021​22​​23​​123​​22​​21​​xπ67π​45π​34π​23π​35π​47π​611π​​sin(x)0−21​−22​​−23​​−1−23​​−22​​−21​​​
=22​​
=(−1)22​​−0⋅22​​
Simplify=−22​​
=−22​​cos(x)
Multiply fractions: a⋅cb​=ca⋅b​=−22​cos(x)​
=−22​cos(x)​−sin(45π​)sin(x)
sin(45π​)sin(x)=−22​sin(x)​
sin(45π​)sin(x)
sin(45π​)=−22​​
sin(45π​)
Rewrite using trig identities:sin(π)cos(4π​)+cos(π)sin(4π​)
sin(45π​)
Write sin(45π​)as sin(π+4π​)=sin(π+4π​)
Use the Angle Sum identity: sin(s+t)=sin(s)cos(t)+cos(s)sin(t)=sin(π)cos(4π​)+cos(π)sin(4π​)
=sin(π)cos(4π​)+cos(π)sin(4π​)
Use the following trivial identity:sin(π)=0
sin(π)
sin(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​sin(x)021​22​​23​​123​​22​​21​​xπ67π​45π​34π​23π​35π​47π​611π​​sin(x)0−21​−22​​−23​​−1−23​​−22​​−21​​​
=0
Use the following trivial identity:cos(4π​)=22​​
cos(4π​)
cos(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​cos(x)123​​22​​21​0−21​−22​​−23​​​xπ67π​45π​34π​23π​35π​47π​611π​​cos(x)−1−23​​−22​​−21​021​22​​23​​​​
=22​​
Use the following trivial identity:cos(π)=(−1)
cos(π)
cos(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​cos(x)123​​22​​21​0−21​−22​​−23​​​xπ67π​45π​34π​23π​35π​47π​611π​​cos(x)−1−23​​−22​​−21​021​22​​23​​​​
=(−1)
Use the following trivial identity:sin(4π​)=22​​
sin(4π​)
sin(x) periodicity table with 2πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​sin(x)021​22​​23​​123​​22​​21​​xπ67π​45π​34π​23π​35π​47π​611π​​sin(x)0−21​−22​​−23​​−1−23​​−22​​−21​​​
=22​​
=0⋅22​​+(−1)22​​
Simplify=−22​​
=−22​​sin(x)
Multiply fractions: a⋅cb​=ca⋅b​=−22​sin(x)​
=−22​cos(x)​−(−22​sin(x)​)
Apply rule −(−a)=a=−22​cos(x)​+22​sin(x)​
Since the denominators are equal, combine the fractions: ca​±cb​=ca±b​=2−2​cos(x)+2​sin(x)​
Factor out common term 2​=22​(−cos(x)+sin(x))​
Cancel 22​(−cos(x)+sin(x))​:2​−cos(x)+sin(x)​
22​(−cos(x)+sin(x))​
Apply radical rule: 2​=221​=2221​(sin(x)−cos(x))​
Apply exponent rule: xbxa​=xb−a1​21221​​=21−21​1​=21−21​−cos(x)+sin(x)​
Subtract the numbers: 1−21​=21​=221​−cos(x)+sin(x)​
Apply radical rule: 221​=2​=2​−cos(x)+sin(x)​
=2​−cos(x)+sin(x)​
Rationalize 2​−cos(x)+sin(x)​:22​(sin(x)−cos(x))​
2​−cos(x)+sin(x)​
Multiply by the conjugate 2​2​​=2​2​(−cos(x)+sin(x))2​​
2​2​=2
2​2​
Apply radical rule: a​a​=a2​2​=2=2
=22​(−cos(x)+sin(x))​
=22​(sin(x)−cos(x))​
=22​(−cos(x)+sin(x))​
22​(−cos(x)+sin(x))​+22​(−cos(x)+sin(x))​=0
Simplify 22​(−cos(x)+sin(x))​+22​(−cos(x)+sin(x))​:2​(sin(x)−cos(x))
22​(−cos(x)+sin(x))​+22​(−cos(x)+sin(x))​
Apply rule ca​±cb​=ca±b​=22​(sin(x)−cos(x))+2​(sin(x)−cos(x))​
Add similar elements: 2​(sin(x)−cos(x))+2​(sin(x)−cos(x))=22​(sin(x)−cos(x))=222​(sin(x)−cos(x))​
Divide the numbers: 22​=1=2​(sin(x)−cos(x))
2​(sin(x)−cos(x))=0
Divide both sides by cos(x),cos(x)=0cos(x)2​(sin(x)−cos(x))​=cos(x)0​
Simplifycos(x)2​sin(x)​−2​=0
Use the basic trigonometric identity: cos(x)sin(x)​=tan(x)2​tan(x)−2​=0
2​tan(x)−2​=0
Move 2​to the right side
2​tan(x)−2​=0
Add 2​ to both sides2​tan(x)−2​+2​=0+2​
Simplify2​tan(x)=2​
2​tan(x)=2​
Divide both sides by 2​
2​tan(x)=2​
Divide both sides by 2​2​2​tan(x)​=2​2​​
Simplifytan(x)=1
tan(x)=1
General solutions for tan(x)=1
tan(x) periodicity table with πn cycle:
x06π​4π​3π​2π​32π​43π​65π​​tan(x)033​​13​±∞−3​−1−33​​​​
x=4π​+πn
x=4π​+πn

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Frequently Asked Questions (FAQ)

  • What is the general solution for cos((5pi)/4+x)+sin((5pi)/4-x)=0 ?

    The general solution for cos((5pi)/4+x)+sin((5pi)/4-x)=0 is x= pi/4+pin
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