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Pythagorean Identity

Main definitions and formulas:

• The arcsine function, also known as the inverse sine function, is a function that, for each x between -1 and 1, produces an angle θ between − (π /2) and (π /2) whose sine is x. If arcsinx = θ , then sinθ = x. It is sometimes written sin^{− 1}x, but this notation is misleading because it could also be interpreted as [1/(sinx)], which is different from arcsinx.
• The arccosine function, also known as the inverse cosine function, is a function that, for each x between -1 and 1, produces an angle θ between 0 and π whose cosine is x. If arccosx = θ , then cosθ = x. It is sometimes written cos^{− 1}x, but this notation is misleading because it could also be interpreted as [1/(cosx)], which is different from arccosx.
• The arctangent function, also known as the inverse tangent function, is a function that, for each x, produces an angle θ between − (π/2) and (π/2) whose tangent is x. If arctanx = θ , then tanθ = x. It is sometimes written tan^{− 1}x, but this notation is misleading because it could also be interpreted as [1/(tanx)], which is different from arctanx.