Trigonometry Proof: cos (x + y) = cos x cos y – sin x sin y, Hindi Explanation Trig Formula Class 11

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DERIVATION cos (x + y) = cos x cos y – sin x sin y

#Trigonometry Proof: cos (x + y) = cos x cos y – sin x sin y

#cos(x+y)=cosxcosy–sinxsin y
#mathclass11

MANY MORE ARE THERE IN THE PLAYLIST. PLEASE PLEASE CHECK ONCE. YOU WILL BE AMAZED TO SEE THE QUESTIONS.

In all these videos on Trigonometric Functions I have always focused on explaining the basics and then solving the questions. My way of solving question will always refer back to the basics explained previously so that students can make the connect between basics and application of them.

Lets start:
Arc/ Angle and Radian
Relation between Degree and Radian
Radian measure/ Degree measure
If x increase or decreases by the integral multiple of 2\mathbit{\pi}, the value of sine or cosine functions do not change
sin(2n\mathbit{\pi} + x) = sinx , n \in Z
cos(2n\mathbit{\pi} + x) = cosx , n \in Z cos x = 0, if x = 0, \pm\mathbit{\pi}/2, \pm\mathbf{3}\mathbit{\pi}/2, \pm\mathbf{5}\mathbit{\pi}/2,……i.e.., when x is an odd multiple of \mathbit{\pi}/2 .
cos x = 0 implies x = (2n + 1) \frac{\mathbit{\pi}}{\mathbf{2}}, where n is an integer
sin x = 0, if x = 0, \pm\mathbit{\pi}, \pm\mathbf{2}\mathbit{\pi}, \pm\mathbf{3}\mathbit{\pi},……i.e.., when x is an integral multiple of \mathbit{\pi} .
Sin x = 0 implies x = n\mathbit{\pi}, where n is an integer
Sign of Trigonometric Functions
Cos (x + y) = cos x cos y – sin x sin y
Principal Solutions
General Solutions
Principal Solutions:
Given x value has solutions which are less than 2\mathbit{\pi} and more than or equal to 0, those solutions are called principal solutions:

Sets, Relations and Functions, Trigonometric Functions, Permutations and Combinations, Linear Inequality, Binomial Theorem, Straight Lines, Conic Sections.

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Cos (x + y) = cos x cos y – sin x sin y

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