An equation involving trigonometric ratios of an angle is called a trigonometric identity if it is true for all values of the angle.

**Points to Remember**

·
An equation involving trigonometric ratios of an angle is called a
trigonometric** **identity if it is true
for all values of the angle.

·
Trigonometric identities

(i) sin ^{2} θ + cos^{2} θ = 1

(ii) 1 + tan ^{2} θ = sec^{2} θ

(iii) 1 + cot^{2} θ = cosec^{2} *θ*

·
The line of sight is the line drawn from the eye of an observer to
the point in the** **object viewed by the
observer.

·
The angle of elevation of an object viewed is the angle formed by
the line of sight** **with the horizontal when
it is above the horizontal level.

·
The angle of depression of an object viewed is the angle formed by
the line of sight** **with the horizontal when
it is below the horizontal level.

·
The height or length of an object or distance between two distant
objects can be** **determined with the help
of trigonometric ratios.

Tags : Trigonometry | Mathematics Trigonometry | Mathematics

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