Key Notes
Chapter-09
Some Application to Trigonometry
• The height or length of an object or the distance between two distant objects can be
determined with the help of trigonometric ratio.
• The line of sight is the line drawn from the eye of an observer to the point of the object
viewed by the observer.
• Trigonometric Ratios: In ∆ABC, ∠B = 90o , for angle ' A '
Perpendicular Base P erpendicular
Sin A = , Cos A = , tan A =
Hypotenuse Hypotenuse Base
Base Hypotenuse Hypotenuse
Cot A = , Sec A = , cos ec A =
Perpendicular Base Perpendicular
• Reciprocal Relations:
1 1
sin θ = , cos ec θ =
cos ec θ sin θ
1 1
cos θ = , s ec θ =
s ec θ cos θ
1 1
tan θ = , cot θ =
cot θ tan θ
• Quotient Relations:
sin θ cos θ
tan θ = , cot θ =
cos θ sin θ
• Identities: sin 2 + cos 2 = 1 ⇒ sin 2 θ = 1 – cos 2θ and cos 2 θ = 1 – sin 2 θ
Material downloaded from http://www.ncertsolutions.in
Portal for CBSE Notes, Test Papers, Sample Papers, Tips and Tricks
Chapter-09
Some Application to Trigonometry
• The height or length of an object or the distance between two distant objects can be
determined with the help of trigonometric ratio.
• The line of sight is the line drawn from the eye of an observer to the point of the object
viewed by the observer.
• Trigonometric Ratios: In ∆ABC, ∠B = 90o , for angle ' A '
Perpendicular Base P erpendicular
Sin A = , Cos A = , tan A =
Hypotenuse Hypotenuse Base
Base Hypotenuse Hypotenuse
Cot A = , Sec A = , cos ec A =
Perpendicular Base Perpendicular
• Reciprocal Relations:
1 1
sin θ = , cos ec θ =
cos ec θ sin θ
1 1
cos θ = , s ec θ =
s ec θ cos θ
1 1
tan θ = , cot θ =
cot θ tan θ
• Quotient Relations:
sin θ cos θ
tan θ = , cot θ =
cos θ sin θ
• Identities: sin 2 + cos 2 = 1 ⇒ sin 2 θ = 1 – cos 2θ and cos 2 θ = 1 – sin 2 θ
Material downloaded from http://www.ncertsolutions.in
Portal for CBSE Notes, Test Papers, Sample Papers, Tips and Tricks
