With reference to the origin O, the point A has position vector . The plane and the line have equations and respectively, where , and are parameters and is a real value.
- (a)
It is given that and intersect at a point.
- (i)
Find the range of values of .
- (ii)
Find, in terms of , the coordinates of the point of intersection, , of and .
- (i)
- (b)
It is given that lies on .
- (i)
Show that .
- (ii)
Find the position vector of the foot of perpendicular, , of onto .
- (iii)
Find the cartesian equation of another line through , that lies on the plane containing , and , and makes the same angle with as makes with .
- (i)
It won't just hand you the answer — it asks where you're stuck.How the checker works
Worked solution
10(a)(i)
1. Find the normal vector and Cartesian equation of the plane $\pi$.
The normal vector to the plane is the cross product of its direction vectors:
Taking a simpler parallel normal vector , the Cartesian equation of the plane is:
2. Substitute the equation of line $l$ into the plane equation to find the intersection condition.
Substitute the equation of , , into the plane equation:
Since is eliminated and we obtain (which yields a unique solution ), a unique point of intersection exists regardless of the value of . Thus, can be any real number.
10(a)(ii)
1. Find the scalar product equation of the plane $\pi$ by calculating its normal vector.
The normal vector to the plane is the cross product of its two direction vectors:
Taking the normal vector as , the scalar product equation of is:
2. Substitute the equation of line $l$ into the plane equation to find the intersection point $B$.
Substitute the vector equation of line into the scalar product equation of :
Substitute back into the equation of line to find the position vector of :
The coordinates of are .
10(b)(i)
1. Equate the position vector of point $A$ to the equation of line $l$.
2. Solve for $\beta$ using the $x$-component and substitute into the $y$-component to find $t$.
From the -components:
(Checking with -components: , consistent.)
From the -components:
Substitute :
Shown
10(b)(ii)
1. Find a normal vector to the plane $\pi$.
The normal vector can be found using the cross product of the two direction vectors of the plane :
Taking a simpler parallel vector by dividing by , we use .
2. Formulate the scalar product equation of the plane and the vector equation of the normal line through $A$.
The equation of plane is .
The normal line passing through perpendicular to has the equation:
3. Substitute the line equation into the plane equation to find the foot of the perpendicular, $F$.
Substitute into the equation of :
Substitute back into the line equation to find the position vector of :
10(b)(iii)
1. Concisely recover the coordinates of intersection point $B$ and foot of perpendicular $F$ from earlier parts.
The normal to is , so has equation .
Substituting (with ) into : .
Thus, has position vector .
The line passes through and is parallel to , so .
Substituting into : .
Thus, has position vector .
2. Use the geometric properties of the plane $ABF$ to determine the point $B'$ where line $m$ intersects $\pi$.
Since line lies on the plane containing , and , and makes the same angle with as , must intersect the line (the projection of on ) at a point .
Because , forms an isosceles triangle with altitude . Hence, is the midpoint of .
3. Find the direction vector of $m$ and deduce its cartesian equation.
The direction vector of is given by :
To simplify the direction vector, we can factor out a scalar multiplier. Multiplying by gives an integer direction vector:
Using point and direction vector , the cartesian equation for is:
AI analysis — may contain mistakes.
Worked this one out on paper? Snap your steps and Gigle's AI math checker will circle the step where it went wrong.
More questions on this topic
- 1The lines and have equations …
- 2A drilling company plans to install a straight pipeline through a mountain. Points are defined relative…
- 3A plane has equation . A line passes through the points and with position vectors …
- 4The planes and have vector equations …
- 5A home interior designer is looking to design a pull-down wardrobe lift. To test his concept, the designer built a small…