## Trigonometry (11th Edition) Clone

$$t\approx0.21$$
$$V=\cos2\pi t$$ where $t\in[0,\frac{1}{2}]$ As $V=0.25$, we would have the equation: $$\cos2\pi t=0.25=\frac{1}{4}$$ So, $$2\pi t=\cos^{-1}\frac{1}{4}\approx1.318 (rad)$$ (be careful about radians and degrees) $$t=\frac{1.318}{2\pi}$$ $$t\approx0.21$$ $t\approx0.21$ is the result of this question.