Proof of three trigonometric identities 🔥 sin 3x, cos 3x and tan 3x 🔥 by

Hey Students!!! 🧑‍🎓 🥳 🤠 👏 👩‍🎓
In this tutorial you will learn the proof of three very important trigonometric identity:
1) sin 3x = 3 sin x - 4 sin³ x
2) cos 3x = 4 cos³ x - 3 cos x
3) tan 3x = (3 tan x - tan³ x) /(1 - 3 tan²x).
where x, 3x ≠ (2n + 1) π/2, n is an integer or x, 3x ≠ nπ + π/2, n is an integer

There are actually two conditions regarding the angles for the third identity. In this tutorial I have explained and mentioned the other equally important condition about the angle x as well. Hope this will help students understand such questions better.

This identity can also be written as
1) sin 3θ = 3 sin θ - 4 sin³ θ
2) cos 3θ = 4 cos³ θ - 3 cos θ
3) tan 3θ = (3 tan θ - tan³ θ) /(1 - 3 tan²θ).
where θ, 3θ ≠ (2n + 1) π/2, n is an integer or θ, 3θ ≠ nπ + π/2, n is an integer
or
1) sin 3theta = 3 sin theta - 4 sin³ theta
2) cos 3theta = 4 cos³ theta - 3 cos theta
3) tan 3theta = (3 tan theta - tan³ theta) /(1 - 3 tan²theta).
where theta, 3theta ≠ (2n + 1) π/2, n is an integer or theta, 3theta ≠ nπ + π/2, n is an integer

00:00 What' in it
00:31 Proof of sin 3x = 3 sin x - 4 sin³ x
03:45 Proof of cos 3x = 4 cos³ x - 3 cos x
06:36 Proof of tan 3x = (3 tan x - tan³ x) /(1 - 3 tan²x)
10:13 About the restricted angles

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