If the line joining the points `(_x_1, y_1) and (x_2, y_2)` subtends a right angle at the point (1,1), then `x_1 + x_2 + y_2 + y_2` is equal to

If the line joining the points (x_(1),y_(1)) and (x_(1),y_(1)) subtends a right angle at the point (1,1) then

A line joining the points (1,1,1) and (2,2,2) intersect the plane x+y+z=9 at the point

If the line segment joining the points P(x_1, y_1)a n d Q(x_2, y_2) subtends an angle alpha at the origin O, prove that : O PdotO Q cosalpha=x_1x_2+y_1y_2dot

If the line segment joining the points P(x_1, y_1)a n d\ Q(x_2, y_2) subtends an angle alpha at the origin O, prove that : O PdotO Q\ cosalpha=x_1x_2+y_1y_2dot

If theta\ is the angle which the straight line joining the points (x_1, y_1)a n d\ (x_2, y_2) subtends at the origin, prove that tantheta=(x_2y_1-x_1y_2)/(x_1x_2+y_1y_2)\ a n dcostheta=(x_1x_2+y_1y_2)/(sqrt(x1 2+y1 2x2 2+y2 2))

If theta\ is the angle which the straight line joining the points (x_1, y_1)a n d\ (x_2, y_2) subtends at the origin, prove that tantheta=(x_2y_1-x_1y_2)/(x_1x_2+y_1y_2)\ a n dcostheta=(x_1x_2+y_1y_2)/(sqrt(x1 2 x2 2+y2 2x1 2+y1 2x2 2+ y1 2y2 2))

If chords of contact of the tangent from two points (x_1,y_1) and (x_2,y_2) to the ellipse x^2/a^2+y^2/b^2=1 are at right angles , then (x_1x_2)/(y_1y_2) is equal to

The co-ordinates of the mid points joining P(x_1,y_1) and Q(x_2,y_2) is….