Remember that the unit circle has a radius of 1. In other words, every point on the unit circle is a distance of exactly 1 unit away from the origin, (0,0). Knowing that, you can use the distance formula to find your missing coordinate:
[tex]\sqrt[]{(x_2-x_1)^2+(y_2-y_1)^2_{}}\text{ = Distance = 1}[/tex]
We get,
[tex]\sqrt[]{(0-x)^2+(0-\frac{3}{4})^2_{}}\text{ = 1}[/tex][tex]\sqrt[]{(x)^2+(\frac{3}{4})^2_{}}\text{ = 1}[/tex][tex]\sqrt[]{x^2+\frac{9}{16}^{}_{}}\text{ = 1}[/tex][tex](\sqrt[]{x^2+\frac{9}{16}^{}_{}})^2=(1)^2[/tex][tex]x^2^{}+\frac{9}{16}^{}_{}=1[/tex][tex]x^2=1\text{ - }\frac{9}{16}^{}_{}[/tex][tex]x^2=\frac{7}{16}^{}_{}[/tex][tex]\sqrt{x^2}=\sqrt{\frac{7}{16}^{}_{}}[/tex][tex]\text{ x = }\pm\text{ }\frac{\sqrt[]{7}}{4}[/tex]
Since the x, 3/4 falls on the second quadrant, x is a negative value.
Therefore,
[tex]\text{ x = -}\frac{\sqrt[]{7}}{4}[/tex]
