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### Course: Class 11 Math (India) - Hindi > Unit 3

Lesson 3: Trigonometric identities: Symmetry# Sine and cosine identities symmetry (Hindi)

In this video, we'll find several trigonometric identities for sine and cosine by considering horizontal and vertical symmetries of the unit circle.

## Want to join the conversation?

- How can sin be negative ??

I mean that- how can the length of a side of the triangle be negative, we know that length can never be negative then How we happened to find trigonometric ratios to be negative ?(1 vote) - I have a question - our school teacher said that in different quadrants sin, cos, tan, and their inverse have different signs.

my question is WHY??

please clear my doubt.(1 vote)