What is the value of cos^2(120)-sin^2(120) ?

The value of cos^2(120)-sin^2(120) is -1/2

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cos^2(120)-sin^2(120)

cos^{2} (12 0^{\circ}) - sin^{2} (12 0^{\circ})

- \frac{1}{2}

Solution steps

cos^{2} (12 0^{\circ}) - sin^{2} (12 0^{\circ})

Use the following trivial identity:

cos (12 0^{\circ}) = - \frac{1}{2}

Use the following trivial identity:

sin (12 0^{\circ}) = \frac{3}{2}

= (- \frac{1}{2})^{2} - (\frac{3}{2})^{2}

Simplify

(- \frac{1}{2})^{2} - (\frac{3}{2})^{2} : - \frac{1}{2}

= - \frac{1}{2}

sin (arccos (\frac{2}{5}))

arcsin (0.91)

arcsin (0.72)

arcsin (0.46)

arcsin (\frac{3}{6})

What is the value of cos^2(120)-sin^2(120) ?
The value of cos^2(120)-sin^2(120) is -1/2