This is a free lesson from our course in Trigonometry This lesson introduces and walks you through the Trigonometric Identities. You'll learn it with the help of some examples, practice questions with solution, and watching video as well as explanations by the instructor in their hand writing. The trigonometric identities are equalities that involve trigonometric functions that are true for every single value of the occurring variables.Here you'll learn how these identities are useful when expressions involving trigonometric functions need to be simplified and put into application. (More text below video...)
Other useful lessons:
 Pythagorean Trigonometric Identity Verifying Trigonometric Identities
(Continued from above) Some of the important trigonometric identities are:
Reciprocal Identities:
csc = 1/sin sin = 1/csc sec = 1/cos cos = 1/sec tan = 1/cot cot = 1/tan Tangent and Cotangent Identities:
tan =  sin /cos cot =  cos /sin Pythagorean Identities:
sin2 + cos2 = 1
tan2 + 1 = sec2 1 + cot2 = csc2 Even/Odd Identities
sin (- ) = - sin cos(- ) = cos tan (- ) = - tan Sum and Difference Identities
Sin(A-B) = sin A cos B � cos A sin B
Cos(A-B)= cos A cos B + sin A Sin B

Double Angle Identities
Sin2 = 2 sin cos cos 2 = cos2 � sin2 = 2cos2 -1=1- 2 sin2 tan2 = 2tan /1-tan2 Winpossible's online math courses and tutorials have gained rapidly popularity since their launch in 2008. Over 100,000 students have benefited from Winpossible's courses... these courses in conjunction with free unlimited homework help serve as a very effective math-tutor for our students.
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