Why does sine squared plus cosine squared equal 1?

PreCalculus - Trigonometry: Trig Identities (31 of 57) Proof cos^2(x)=(1+cos2x)/2

Integral 1/cos^2(x)

PreCalculus - Trigonometry: Trig Identities (30 of 57) Proof sin^2(x)=(1-cos2x)/2

Prove (1-cos^2x)/sinx=sinx

Simplify Trig Expression (1-cos(2x))/sin(x) - Find an Identity

Where do Sin, Cos and Tan Actually Come From - Origins of Trigonometry - Part 1

cos^2(1 + tan^2) = 1

Radians in less than 18 minutes • A-Level Maths, Pure Year 2, Chapter 5 📚

Derive an identity for cos(2theta), done fast in 56 seconds

1+cosx=2cos^2(x/2) trigonometry identites solve || 1+cos(theta)

Integral of (1 - cos 2x)/(1 + cos 2x)

1-cosx = 2sin^2(x/2) trigonometric identites proof || 1-cos theta

` cos 1^(@) + cos2^(@) + cos 3^(@) + ….+cos 180^(@)` is equal to

Prove that trigonometry sin^2 A= (1-cos2A)/2 & cos^2 A= (1+cos2A)/2 PART-8

Prove that 1+cosx=2cos^2(x/2) and 1-cosx=2sin^2(x/2) trigonometric identites

(1 - cos^2)(1+ cot^2) = 1

Evaluating Inverse Trigonometric Functions

Find the limit as x approaches 0 of (1- cos 2x)/(2 sin^2 x)

1 - cos2x | 1 - cos(2x) | Identity for 1 - cos2x | Proof of 1 - cos2x formula | Value of 1 - cos2x