Trigonometric Formulas Identities
Trigonometric Formulas Identities
Trigonometric Formulas Identities
A. Reciprocal Relations
& &
sin 𝐴 = csc 𝐴 =
'(' ) (+, )
& &
cos 𝐴 = (.' ) sec 𝐴 = '0( )
& &
tan 𝐴 = '03 ) cot 𝐴 = 34, )
B. Pythagorean Relations
sin5 𝐴 + cos 5 𝐴 = 1
tan5 𝐴 + 1 = sec 5 𝐴
cot 5 𝐴 + 1 = csc 5 𝐴
C. By Definition
(+, ) '0( )
tan 𝐴 = '0( ) cot 𝐴 = (+, )
= 2 cos 5 𝐴 − 1
= 1 − 2 sin5 𝐴
2 tan 𝐴
tan 2𝐴 =
1 − tan5 𝐴
cot 5 𝐴 − 1
cot 2𝐴 =
2 cot 𝐴
F. Functions of Half-Angle
1 1 − cos 𝐴
sin 𝐴 = ±?
2 2
1 1 + cos 𝐴
cos 𝐴 = ±?
2 2