Question

For \[y\in\left(-\frac{\pi}{2},\frac{\pi}{2}\right)\], which value of \[\cos y\] follows from \[\cos^2y=1-x^2\]?

विकल्प

• \[\cos y=1-x^2\]

• \[\cos y=-\sqrt{1-x^2}\]

• \[\cos y=\sqrt{1-x^2}\]

• \[\cos y=\sqrt{x^2-1}\]

Answer 1

For \[y\in\left(-\frac{\pi}{2},\frac{\pi}{2}\right)\], \[\cos y\] is positive. Therefore the positive square root is selected: \[\cos y=\sqrt{1-x^2}\].