FIND A COTERMINAL ANGLE BETWEEN 0 AND 2PIE

Coterminal angles are angles that have the same initial side and the same terminal sides. We determine coterminal angle of a given angle by adding or subtracting 360° or  2π.

Find a coterminal angle between 0 and 2π for each given angle.

Problem 1 :

5𝜋2

Solution :

Positive angle that is coterminal with 5π/2 :

5𝜋2 + 2𝜋 = 5𝜋2 + 4𝜋25𝜋2 + 2𝜋 = (5𝜋 + 4𝜋)25𝜋2 + 2𝜋 = 9𝜋2

So, positive angle that is coterminal with 5π/2 is 9π/2.

Negative angle that is coterminal with 5π/2 :

5𝜋2 - 2𝜋 = 5𝜋2 - 4𝜋25𝜋2 - 2𝜋 = (5𝜋 - 4𝜋)25𝜋2 - 2𝜋 = 𝜋2

So, negative angle that is coterminal with 5π/2 is π/2.

Problem 2 :

71𝜋12

Solution :

Positive angle that is coterminal with 71π/12 :

71𝜋12 + 2𝜋 = 71𝜋12 + 24𝜋1271𝜋12 + 2𝜋 = (71𝜋 + 24𝜋)1271𝜋12 + 2𝜋 = 95𝜋12

So, positive angle that is coterminal with 71π/12 is 95π/12.

Negative angle that is coterminal with 71π/12 :

71𝜋12 - 2𝜋 = 71𝜋12 - 24𝜋1271𝜋12 - 2𝜋 = (71𝜋 - 24𝜋)1271𝜋12 - 2𝜋 = 47𝜋12

So, negative angle that is coterminal with 71π/12 is 47π/12.

Problem 3 :

23𝜋6

Solution :

Positive angle that is coterminal with 23π/6 :

23𝜋6 + 2𝜋 = 23𝜋6 + 12𝜋623𝜋6 + 2𝜋 = (23𝜋 + 12𝜋)623𝜋6 + 2𝜋 = 35𝜋6

So, negative angle that is coterminal with 23π/6 is 35π/6.

Negative angle that is coterminal with 23π/6 :

23𝜋6 - 2𝜋 = 23𝜋6 - 12𝜋623𝜋6 - 2𝜋 = (23𝜋 - 12𝜋)623𝜋6 - 2𝜋 = 11𝜋6

So, negative angle that is coterminal with 23π/6 is 11π/6.

Problem 4 :

-17𝜋36

Solution :

Positive angle that is coterminal with -17π/36 :

-17𝜋36 + 2𝜋 = -17𝜋36 + 72𝜋36-17𝜋36 + 2𝜋 = (-17𝜋 + 72𝜋)36-17𝜋36 + 2𝜋 = 55𝜋36

So, positive angle that is coterminal with -17π/36 is 55π/36.

Negative angle that is coterminal with -17π/36 :

-17𝜋36 - 2𝜋 = -17𝜋36 - 72𝜋36-17𝜋36 - 2𝜋 = (-17𝜋 - 72𝜋)36-17𝜋36 - 2𝜋 = -89𝜋36

So, negative angle that is coterminal with -17π/36 is -89π/36.

Problem 5 :

65𝜋12

Solution :

Positive angle that is coterminal with 65π/12 :

65𝜋12 + 2𝜋 = 65𝜋12 + 24𝜋1265𝜋12 + 2𝜋 = (65𝜋 + 24𝜋)1265𝜋12 + 2𝜋 = 89𝜋12

So, positive angle that is coterminal with 65π/12 is 89π/12.

Negative angle that is coterminal with 65π/12 :

65𝜋12 - 2𝜋 = 65𝜋12 - 24𝜋1265𝜋12 - 2𝜋 = (65𝜋 - 24𝜋)1265𝜋12 - 2𝜋 = 41𝜋12

So, negative angle that is coterminal with 65π/12 is 41π/12.

Problem 6 :

124𝜋45

Solution :

Positive angle that is coterminal with 124π/45 :

124𝜋45 + 2𝜋 = 124𝜋45 + 90𝜋45124𝜋45 + 2𝜋 = (124𝜋 + 90𝜋)45124𝜋45 + 2𝜋 = 214𝜋45

So, positive angle that is coterminal with 124π/45 is 214π/45.

Negative angle that is coterminal with 124π/45 :

124𝜋45 - 2𝜋 = 124𝜋45 - 90𝜋45124𝜋45 - 2𝜋 = (124𝜋 - 90𝜋)45124𝜋45 - 2𝜋 = 34𝜋45

So, negative angle that is coterminal with 124π/45 is 34π/45.

Problem 7 :

-23𝜋12

Solution :

Positive angle that is coterminal with -23π/12 :

-23𝜋12 + 2𝜋 = -23𝜋12 + 24𝜋12-23𝜋12 + 2𝜋 = (-23𝜋 + 24𝜋)12-23𝜋12 + 2𝜋 = 𝜋12

So, positive angle that is coterminal with -23π/12 is π/12.

Negative angle that is coterminal with -23π/12 :

-23𝜋12 - 2𝜋 = -23𝜋12 - 24𝜋12-23𝜋12 - 2𝜋 = (-23𝜋 - 24𝜋)12-23𝜋12 - 2𝜋 = -47𝜋12

So, negative angle that is coterminal with -23π/12 is -47π/12.

Problem 8 :

31𝜋12

Solution :

Positive angle that is coterminal with 31π/12 :

31𝜋12 + 2𝜋 = 31𝜋12 + 24𝜋1231𝜋12 + 2𝜋 = (31𝜋 + 24𝜋)1231𝜋12 + 2𝜋 = 55𝜋12

So, positive angle that is coterminal with 31π/12 is 55π/12.

Negative angle that is coterminal with 31π/12 :

31𝜋12 - 2𝜋 = 31𝜋12 - 24𝜋1231𝜋12 - 2𝜋 = (31𝜋 - 24𝜋)1231𝜋12 - 2𝜋 = 7𝜋12

So, negative angle that is coterminal with 31π/12 is 7π/12.

Problem 9 :

-7𝜋12

Solution :

Positive angle that is coterminal with -7π/12 :

-7𝜋12 + 2𝜋 = -7𝜋12 + 24𝜋12-7𝜋12 + 2𝜋 = (-7𝜋 + 24𝜋)12-7𝜋12 + 2𝜋 = 17𝜋12

So, positive angle that is coterminal with -7π/12 is 17π/12.

Negative angle that is coterminal with -7π/12 :

-7𝜋12 - 2𝜋 = -7𝜋12 - 24𝜋12-7𝜋12 - 2𝜋 = (-7𝜋 - 24𝜋)12-7𝜋12 - 2𝜋 = -31𝜋12

So, negative angle that is coterminal with -7π/12 is -31π/12.

Problem 10 :

35𝜋12

Solution :

Positive angle that is coterminal with 35π/12 :

35𝜋12 + 2𝜋 = 35𝜋12 + 24𝜋1235𝜋12 + 2𝜋 = (35𝜋 + 24𝜋)1235𝜋12 + 2𝜋 = 69𝜋12

So, positive angle that is coterminal with 35π/12 is 69π/12.

Negative angle that is coterminal with 35π/12 :

35𝜋12 - 2𝜋 = 35𝜋12 - 24𝜋1235𝜋12 - 2𝜋 = (35𝜋 - 24𝜋)1235𝜋12 - 2𝜋 = 11𝜋12

So, negative angle that is coterminal with 35π/12 is 11π/12.

Problem 11 :

-5𝜋4

Solution :

Positive angle that is coterminal with -5π/4 :

-5𝜋4 + 2𝜋 = -5𝜋4 + 8𝜋4-5𝜋4 + 2𝜋 = (-5𝜋 + 8𝜋)4-5𝜋4 + 2𝜋 = 3𝜋4

So, positive angle that is coterminal with -5π/4 is 3π/4.

Negative angle that is coterminal with -5π/4 :

-5𝜋4 - 2𝜋 = -5𝜋4 - 8𝜋4-5𝜋4 - 2𝜋 = (-5𝜋 - 8𝜋)4-5𝜋4 - 2𝜋 = -13𝜋4

So, negative angle that is coterminal with -5π/4 is -13π/4.

Problem 12 :

22𝜋9

Solution :

Positive angle that is coterminal with 22π/9 :

22𝜋9 + 2𝜋 = 22𝜋9 + 18𝜋922𝜋9 + 2𝜋 = (22𝜋 + 18𝜋)922𝜋9 + 2𝜋 = 40𝜋9

So, positive angle that is coterminal with 22π/9 is 40π/9.

Negative angle that is coterminal with 22π/9 :

22𝜋9 - 2𝜋 = 22𝜋9 - 18𝜋922𝜋9 - 2𝜋 = (22𝜋 - 18𝜋)922𝜋9 - 2𝜋 = 4𝜋9

So, negative angle that is coterminal with 22π/9 is 4π/9.

Problem 13 :

Solution :

Positive angle that is coterminal with -π :

-π + 2π = π

So, positive angle that is coterminal with -π is π.

Negative angle that is coterminal with -π :

-π - 2π = -3π

So, negative angle that is coterminal with -π is -3π.

Problem 14 :

11𝜋3

Solution :

Positive angle that is coterminal with  11π/3 :

11𝜋3 + 2𝜋 = 11𝜋3 + 6𝜋311𝜋3 + 2𝜋 = (11𝜋 + 6𝜋)311𝜋3 + 2𝜋 = 17𝜋3

So, positive angle that is coterminal with 11π/3 is 17π/3.

Negative angle that is coterminal with 11π/3 :

11𝜋3 - 2𝜋 = 11𝜋3 - 6𝜋311𝜋3 - 2𝜋 = (11𝜋 - 6𝜋)311𝜋3 - 2𝜋 = 5𝜋3

So, negative angle that is coterminal with 11π/3 is 5π/3.

Problem 15 :

-19𝜋45

Solution :

Positive angle that is coterminal with  -19π/45 :

-19𝜋45 + 2𝜋 = -19𝜋45 + 90𝜋45-19𝜋45 + 2𝜋 = (-19𝜋 + 90𝜋)45-19𝜋45 + 2𝜋 = 71𝜋45

So, positive angle that is coterminal with -19π/45 is 71π/45.

Negative angle that is coterminal with -19π/45 :

-19𝜋45 - 2𝜋 = -19𝜋45 - 90𝜋45-19𝜋45 - 2𝜋 = (-19𝜋 - 90𝜋)45-19𝜋45 - 2𝜋 = -109𝜋45

So, negative angle that is coterminal with -19π/45 is -109π/45.

Problem 16 :

11𝜋4

Solution :

Positive angle that is coterminal with  11π/4 :

11𝜋4 + 2𝜋 = 11𝜋4 + 8𝜋411𝜋4 + 2𝜋 = (11𝜋 + 8𝜋)411𝜋4 + 2𝜋 = 19𝜋4

So, positive angle that is coterminal with 11π/4 is 19π/4.

Negative angle that is coterminal with 11π/4 :

11𝜋4 - 2𝜋 = 11𝜋4 - 8𝜋411𝜋4 - 2𝜋 = (11𝜋 - 8𝜋)411𝜋4 - 2𝜋 = 3𝜋4

So, negative angle that is coterminal with 11π/4 is 3π/4.

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