Trigonometric functions of an acute angle
Trigonometric functions are commonly defined as ratios of two sides of a right triangle containing the angle. There are six basic trigonometric functions, which are tabulated here along with equations relating them to one another
Sine: The sine of an angle in a right triangle equals the opposite side divided by the hypotenuse.
Cosine: The cosine of an angle in a right triangle equals the adjacent side divided by the hypotenuse.
Tangent: The tangent is the opposite side divided by the adjacent side.
Cosecant (csc): is the reciprocal of sine, i.e. the ratio of the length of the hypotenuse to the length of the opposite side.
Secant (sec): is the reciprocal of cosine, i.e. the ratio of the length of the hypotenuse to the length of the adjacent side.
Cotangent (cot): is the reciprocal of tan, i.e. the ratio of the length of the adjacent side to the length of the opposite side.
sin A 
= 
opposite
hypotenuse 
= 
a
c 

csc A 
= 
hypotenuse
opposite 
= 
c
a 

cos A 
= 
adjacent
hypotenus 
= 
b
c 

sec A 
= 
hypotenuse
adjacent 
= 
c
a 

tan A

= 
opposite
adjacent 
= 
a
b 

cot A

= 
adjacent
opposite 
= 
b
a 

