Direction Angle, Direction Ratios and Direction Cosine
Three Dimensional Geometry

121132 The direction cosine of a line which is perpendicular to both the lines whose direction ratios are \(-1,2,2\) and \(0,2,1\) are

1 \(\frac{-2}{3}, \frac{1}{3}, \frac{2}{3}\)
2 \(\frac{2}{3}, \frac{-1}{3}, \frac{2}{3}\)
3 \(\frac{2}{3}, \frac{1}{3}, \frac{-2}{3}\)
4 \(\frac{2}{3}, \frac{-1}{3}, \frac{-2}{3}\)
Three Dimensional Geometry

121157 If \(A=(1,8,4), B=(2,-3,1)\), then the direction cosines of a normal to the plane \(A O B\) is

1 \(\frac{2}{\sqrt{78}}, \frac{5}{\sqrt{78}}, \frac{-7}{\sqrt{78}}\)
2 \(\frac{2 \sqrt{10}}{9}, \frac{7 \sqrt{10}}{90}, \frac{-19 \sqrt{10}}{90}\)
3 \(\frac{4}{\sqrt{218}}, \frac{9}{\sqrt{218}}, \frac{-11}{\sqrt{218}}\)
4 \(\frac{2}{11}, \frac{6}{11}, \frac{-9}{11}\)
Three Dimensional Geometry

121181 Let \(6 x-3 y+2 z-6=0\) be the given plane. If a, \(b\) and \(c\) are the intercepts made by the plane on \(\mathrm{X}, \mathrm{Y}\) and \(\mathrm{Z}\)-axes, respectively; \(l, \mathrm{~m}\) and \(\mathrm{n}\) are the direction cosines of a normal drawn to the plane and \(p\) is the perpendicular distance from the origin to the plane, then \( \vert\mathbf{a} l+\mathrm{bm}+\mathbf{c n} \vert=\)

1 \(\mathrm{p}\)
2 \(2 \mathrm{p}\)
3 \(3 \mathrm{p}\)
4 \(4 \mathrm{p}\)
Three Dimensional Geometry

121122 If the line given by \(\overline{\mathbf{r}}=2 \hat{\mathbf{i}}+\lambda(\hat{\mathbf{i}}+2 \hat{\mathbf{j}}+\mathrm{m} \hat{\mathbf{k}})\) and \(\overline{\mathbf{r}}=\hat{\mathbf{i}}+\mu(2 \hat{\mathbf{i}}+\hat{\mathbf{j}}+6 \hat{\mathbf{k}})\) are perpendicular, then the value of \(m\) is

1 \(\frac{-3}{2}\)
2 \(\frac{3}{2}\)
3 \(\frac{-2}{3}\)
4 \(\frac{2}{3}\)
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Three Dimensional Geometry

121132 The direction cosine of a line which is perpendicular to both the lines whose direction ratios are \(-1,2,2\) and \(0,2,1\) are

1 \(\frac{-2}{3}, \frac{1}{3}, \frac{2}{3}\)
2 \(\frac{2}{3}, \frac{-1}{3}, \frac{2}{3}\)
3 \(\frac{2}{3}, \frac{1}{3}, \frac{-2}{3}\)
4 \(\frac{2}{3}, \frac{-1}{3}, \frac{-2}{3}\)
Three Dimensional Geometry

121157 If \(A=(1,8,4), B=(2,-3,1)\), then the direction cosines of a normal to the plane \(A O B\) is

1 \(\frac{2}{\sqrt{78}}, \frac{5}{\sqrt{78}}, \frac{-7}{\sqrt{78}}\)
2 \(\frac{2 \sqrt{10}}{9}, \frac{7 \sqrt{10}}{90}, \frac{-19 \sqrt{10}}{90}\)
3 \(\frac{4}{\sqrt{218}}, \frac{9}{\sqrt{218}}, \frac{-11}{\sqrt{218}}\)
4 \(\frac{2}{11}, \frac{6}{11}, \frac{-9}{11}\)
Three Dimensional Geometry

121181 Let \(6 x-3 y+2 z-6=0\) be the given plane. If a, \(b\) and \(c\) are the intercepts made by the plane on \(\mathrm{X}, \mathrm{Y}\) and \(\mathrm{Z}\)-axes, respectively; \(l, \mathrm{~m}\) and \(\mathrm{n}\) are the direction cosines of a normal drawn to the plane and \(p\) is the perpendicular distance from the origin to the plane, then \( \vert\mathbf{a} l+\mathrm{bm}+\mathbf{c n} \vert=\)

1 \(\mathrm{p}\)
2 \(2 \mathrm{p}\)
3 \(3 \mathrm{p}\)
4 \(4 \mathrm{p}\)
Three Dimensional Geometry

121122 If the line given by \(\overline{\mathbf{r}}=2 \hat{\mathbf{i}}+\lambda(\hat{\mathbf{i}}+2 \hat{\mathbf{j}}+\mathrm{m} \hat{\mathbf{k}})\) and \(\overline{\mathbf{r}}=\hat{\mathbf{i}}+\mu(2 \hat{\mathbf{i}}+\hat{\mathbf{j}}+6 \hat{\mathbf{k}})\) are perpendicular, then the value of \(m\) is

1 \(\frac{-3}{2}\)
2 \(\frac{3}{2}\)
3 \(\frac{-2}{3}\)
4 \(\frac{2}{3}\)
Three Dimensional Geometry

121132 The direction cosine of a line which is perpendicular to both the lines whose direction ratios are \(-1,2,2\) and \(0,2,1\) are

1 \(\frac{-2}{3}, \frac{1}{3}, \frac{2}{3}\)
2 \(\frac{2}{3}, \frac{-1}{3}, \frac{2}{3}\)
3 \(\frac{2}{3}, \frac{1}{3}, \frac{-2}{3}\)
4 \(\frac{2}{3}, \frac{-1}{3}, \frac{-2}{3}\)
Three Dimensional Geometry

121157 If \(A=(1,8,4), B=(2,-3,1)\), then the direction cosines of a normal to the plane \(A O B\) is

1 \(\frac{2}{\sqrt{78}}, \frac{5}{\sqrt{78}}, \frac{-7}{\sqrt{78}}\)
2 \(\frac{2 \sqrt{10}}{9}, \frac{7 \sqrt{10}}{90}, \frac{-19 \sqrt{10}}{90}\)
3 \(\frac{4}{\sqrt{218}}, \frac{9}{\sqrt{218}}, \frac{-11}{\sqrt{218}}\)
4 \(\frac{2}{11}, \frac{6}{11}, \frac{-9}{11}\)
Three Dimensional Geometry

121181 Let \(6 x-3 y+2 z-6=0\) be the given plane. If a, \(b\) and \(c\) are the intercepts made by the plane on \(\mathrm{X}, \mathrm{Y}\) and \(\mathrm{Z}\)-axes, respectively; \(l, \mathrm{~m}\) and \(\mathrm{n}\) are the direction cosines of a normal drawn to the plane and \(p\) is the perpendicular distance from the origin to the plane, then \( \vert\mathbf{a} l+\mathrm{bm}+\mathbf{c n} \vert=\)

1 \(\mathrm{p}\)
2 \(2 \mathrm{p}\)
3 \(3 \mathrm{p}\)
4 \(4 \mathrm{p}\)
Three Dimensional Geometry

121122 If the line given by \(\overline{\mathbf{r}}=2 \hat{\mathbf{i}}+\lambda(\hat{\mathbf{i}}+2 \hat{\mathbf{j}}+\mathrm{m} \hat{\mathbf{k}})\) and \(\overline{\mathbf{r}}=\hat{\mathbf{i}}+\mu(2 \hat{\mathbf{i}}+\hat{\mathbf{j}}+6 \hat{\mathbf{k}})\) are perpendicular, then the value of \(m\) is

1 \(\frac{-3}{2}\)
2 \(\frac{3}{2}\)
3 \(\frac{-2}{3}\)
4 \(\frac{2}{3}\)
Three Dimensional Geometry

121132 The direction cosine of a line which is perpendicular to both the lines whose direction ratios are \(-1,2,2\) and \(0,2,1\) are

1 \(\frac{-2}{3}, \frac{1}{3}, \frac{2}{3}\)
2 \(\frac{2}{3}, \frac{-1}{3}, \frac{2}{3}\)
3 \(\frac{2}{3}, \frac{1}{3}, \frac{-2}{3}\)
4 \(\frac{2}{3}, \frac{-1}{3}, \frac{-2}{3}\)
Three Dimensional Geometry

121157 If \(A=(1,8,4), B=(2,-3,1)\), then the direction cosines of a normal to the plane \(A O B\) is

1 \(\frac{2}{\sqrt{78}}, \frac{5}{\sqrt{78}}, \frac{-7}{\sqrt{78}}\)
2 \(\frac{2 \sqrt{10}}{9}, \frac{7 \sqrt{10}}{90}, \frac{-19 \sqrt{10}}{90}\)
3 \(\frac{4}{\sqrt{218}}, \frac{9}{\sqrt{218}}, \frac{-11}{\sqrt{218}}\)
4 \(\frac{2}{11}, \frac{6}{11}, \frac{-9}{11}\)
Three Dimensional Geometry

121181 Let \(6 x-3 y+2 z-6=0\) be the given plane. If a, \(b\) and \(c\) are the intercepts made by the plane on \(\mathrm{X}, \mathrm{Y}\) and \(\mathrm{Z}\)-axes, respectively; \(l, \mathrm{~m}\) and \(\mathrm{n}\) are the direction cosines of a normal drawn to the plane and \(p\) is the perpendicular distance from the origin to the plane, then \( \vert\mathbf{a} l+\mathrm{bm}+\mathbf{c n} \vert=\)

1 \(\mathrm{p}\)
2 \(2 \mathrm{p}\)
3 \(3 \mathrm{p}\)
4 \(4 \mathrm{p}\)
Three Dimensional Geometry

121122 If the line given by \(\overline{\mathbf{r}}=2 \hat{\mathbf{i}}+\lambda(\hat{\mathbf{i}}+2 \hat{\mathbf{j}}+\mathrm{m} \hat{\mathbf{k}})\) and \(\overline{\mathbf{r}}=\hat{\mathbf{i}}+\mu(2 \hat{\mathbf{i}}+\hat{\mathbf{j}}+6 \hat{\mathbf{k}})\) are perpendicular, then the value of \(m\) is

1 \(\frac{-3}{2}\)
2 \(\frac{3}{2}\)
3 \(\frac{-2}{3}\)
4 \(\frac{2}{3}\)