sinx+sin2x+sin3x+...+sin nx, cosx+cos2x+cos3x+cos 4 x+...+cos nx

More interesting questions:
https://www.youtube.com/playlist?list=PLg9w7tItBlZsC-FFxBJxFg3dkCFGUqXIR

Instagram account: https://www.instagram.com/mathphyen/

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more video lists:
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Probability and discrete mathematics:

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Probability interview questions:

https://www.youtube.com/watch?v=qphhG_1rWf8&list=PLg9w7tItBlZtI1eM6znSYfyDEaqQtUx5b

Probability theory:

https://www.youtube.com/watch?v=8s-nyRLBsDo&list=PLg9w7tItBlZsvciKHBx8lXXnCtQ7Ou4cV

Complex analysis:

https://www.youtube.com/playlist?list=PLg9w7tItBlZsYfYG6dUISItqsSRSXaX4B

Combinatorics:

https://www.youtube.com/playlist?list=PLg9w7tItBlZvQt0YNfCqcULzrPme2ai7K

additive combinatorics:

https://www.youtube.com/playlist?list=PLg9w7tItBlZseUrmXgf_2yc2NI_obVUhB

Calculus and advanced mathematics (abstract algebra):

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Real analysis

https://www.youtube.com/playlist?list=PLg9w7tItBlZumEJ4DacAKgstCvDHKtY63

Reduction formula in Calculus:

https://www.youtube.com/playlist?list=PLg9w7tItBlZubmhgkHoHvje1uOASnkcke

Integrals of trigonometric functions:

https://www.youtube.com/playlist?list=PLg9w7tItBlZuwEER2YvFV06ri6i1Cj3hh

(algebraic geometry)

https://www.youtube.com/playlist?list=PLg9w7tItBlZssQ4Smzgp_bk2rEszKaW0B

Linear algebra Proof:

https://www.youtube.com/playlist?list=PLg9w7tItBlZueH6LMeYzzwPMUlIaRhCZo

Ring theory:

https://www.youtube.com/playlist?list=PLg9w7tItBlZs9w4wrNAuv4oJdrt-sIWUP

Abstract Algebra:
https://www.youtube.com/playlist?list=PLg9w7tItBlZsyZ0Ri0IDPYEwDxDXjCqB0

Group theory:
https://www.youtube.com/playlist?list=PLg9w7tItBlZu4Qkxz2WSk4eYZmDAC8ZY0

Galois theory:
https://www.youtube.com/playlist?list=PLg9w7tItBlZsepuNJ3tOnG238M03KrKaG

number theory and others:

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Riemann Zeta functions:

https://www.youtube.com/playlist?list=PLg9w7tItBlZu4ncqL53iPd1GmwKq8yYoM

Math related to pi:

https://www.youtube.com/playlist?list=PLg9w7tItBlZuzFft3Y5h1LRaNvAv7ruKe

Number theory:

https://www.youtube.com/playlist?list=PLg9w7tItBlZvGgPYrFxfGWaQgQBrLOOws

Set Theory:

https://www.youtube.com/playlist?list=PLg9w7tItBlZsDqBUL-CIHcVVBs9EODL_J

High school math & AP calculus:
https://www.youtube.com/playlist?list=PLg9w7tItBlZv165XaBIyj03q3WSMMUqDo

Solving polynomial equation:

https://www.youtube.com/playlist?list=PLg9w7tItBlZsheN8dz8LLPy99AaLb7_-7

Engineering Mathematics:

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Laplace transformation:

https://www.youtube.com/playlist?list=PLg9w7tItBlZty21VgNOrLTKg3BM1sFmFE

differential equation:

https://www.youtube.com/playlist?list=PLg9w7tItBlZukQ1yQXKXPo4ZN2yMHwvf1

0xab3acdec0919be9d429baf2190de2e2a4a384c7e

Legendre polynomial:

https://www.youtube.com/playlist?list=PLg9w7tItBlZvG3Ju8YUxEct1tawePe_ZA

Complex analysis:

https://www.youtube.com/playlist?list=PLg9w7tItBlZsYfYG6dUISItqsSRSXaX4B

Gamma Function:

https://www.youtube.com/playlist?list=PLg9w7tItBlZvKhQHLzaULPNtZH7mYNIf9

Theoretical Physics:

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Quantum Mechanics:

https://www.youtube.com/playlist?list=PLg9w7tItBlZuP5Wv2jMbeTd7uc9ZXYS6m

Quantum Field Theory:
https://www.youtube.com/playlist?list=PLg9w7tItBlZvvsWqUz6uR85ktsrcv5Y4r

Electrodynamics:

https://www.youtube.com/playlist?list=PLg9w7tItBlZu6oIdAtRaT-Wtjkg3_dJcQ

Quantum Information:

https://www.youtube.com/playlist?list=PLg9w7tItBlZs2JgNL6qxtPSlnWAFkqoJG

Quantum Algorithms:

https://www.youtube.com/playlist?list=PLg9w7tItBlZvyCUpJAskKqpeLkKhrtQio

Theoretical Computer Sciences:

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Complexity Theory:
https://www.youtube.com/playlist?list=PLg9w7tItBlZu5dzTT0xqtLrx-46jCfR4o

Algorithm:
https://www.youtube.com/playlist?list=PLg9w7tItBlZt3SSooTufVJ5tsiJte-nJQ