# Trigonometric Functions-I, Graph of Cos θ as θ Varies from 0 to 2π

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## Graph of Cos Θ as Θ Varies from 0 to 2π

As in the case of , we shall also discuss the changes in the values of when assumes values in the intervals , and

In the interval , point lies in the first quadrant.

Therefore, is positive but decreases from to as increases from to .

Thus in this interval decreases from to .

is positive.

• In the interval , point lies in the second quadrant.

• Therefore point lies on the negative side of x-axis. So in this case is negative and decreases from to as increases from to .

• Thus in this interval decreases from to .

• is negative.

• In the interval , point lies in the third quadrant.

• Therefore, remains negative as it is on the negative side of x-axis.

• Therefore is negative but increases from to as increases from to .

• Hence in this interval increases from to .

• is negative.

• In the interval , point lies in the fourth quadrant.

• Therefore point lies on the positive side of x-axis.

• Therefore is positive and increases from to as increases from to .

• Thus in this interval increases from to .

• is positive.