Given: P ⊃ x − 1 2 = y − 3 3 = z + 2 1 \text{Given: } P \supset \dfrac{x-1}{2} = \dfrac{y-3}{3} = \dfrac{z+2}{1} Given: P ⊃ 2 x − 1 = 3 y − 3 = 1 z + 2
P ⊥ x + 2 y + 3 z = 4 P \perp x + 2y + 3z = 4 P ⊥ x + 2 y + 3 z = 4
P 1 ∥ P , P 1 ∋ ( 4 , 2 , 2 ) P_1 \parallel P, \ P_1 \ni (4,2,2) P 1 ∥ P , P 1 ∋ ( 4 , 2 , 2 )
To find: which of the statements (1)–(4) are TRUE \text{To find: which of the statements (1)--(4) are TRUE} To find: which of the statements (1)–(4) are TRUE
1. find n ⃗ P 1.\ \text{find } \vec{n}_P 1. find n P
2. equation of P 2.\ \text{equation of } P 2. equation of P
3. test each statement 3.\ \text{test each statement} 3. test each statement
d ⃗ = ( 2 , 3 , 1 ) , A ( 1 , 3 , − 2 ) ∈ L \vec{d} = (2, 3, 1), \quad A(1, 3, -2) \in L d = ( 2 , 3 , 1 ) , A ( 1 , 3 , − 2 ) ∈ L
L ⊂ P ⇒ n ⃗ P ⋅ d ⃗ = 0 L \subset P \Rightarrow \vec{n}_P \cdot \vec{d} = 0 L ⊂ P ⇒ n P ⋅ d = 0
P ⊥ ( x + 2 y + 3 z = 4 ) ⇒ n ⃗ P ⋅ ( 1 , 2 , 3 ) = 0 P \perp (x+2y+3z=4) \Rightarrow \vec{n}_P \cdot (1,2,3) = 0 P ⊥ ( x + 2 y + 3 z = 4 ) ⇒ n P ⋅ ( 1 , 2 , 3 ) = 0
n ⃗ P = d ⃗ × ( 1 , 2 , 3 ) = ( 7 , − 5 , 1 ) \vec{n}_P = \vec{d} \times (1,2,3) = (7, -5, 1) n P = d × ( 1 , 2 , 3 ) = ( 7 , − 5 , 1 )
7 ( x − 1 ) − 5 ( y − 3 ) + ( z + 2 ) = 0 7(x-1) - 5(y-3) + (z+2) = 0 7 ( x − 1 ) − 5 ( y − 3 ) + ( z + 2 ) = 0
P : 7 x − 5 y + z = − 10 ⇒ (1) TRUE P:\ 7x - 5y + z = -10 \Rightarrow \text{(1) TRUE} P : 7 x − 5 y + z = − 10 ⇒ (1) TRUE
P 1 : 7 x − 5 y + z = 28 − 10 + 2 = 20 P_1:\ 7x - 5y + z = 28 - 10 + 2 = 20 P 1 : 7 x − 5 y + z = 28 − 10 + 2 = 20
d ( P , P 1 ) = ∣ 20 − ( − 10 ) ∣ 75 = 30 5 3 = 2 3 d(P, P_1) = \dfrac{|20 - (-10)|}{\sqrt{75}} = \dfrac{30}{5\sqrt3} = 2\sqrt3 d ( P , P 1 ) = 75 ∣20 − ( − 10 ) ∣ = 5 3 30 = 2 3
⇒ (2) false (says 30) \Rightarrow \text{(2) false (says 30)} ⇒ (2) false (says 30)
d O = ∣ 10 ∣ 75 = 2 3 = 2 3 3 d_O = \dfrac{|10|}{\sqrt{75}} = \dfrac{2}{\sqrt3} = \dfrac{2\sqrt3}{3} d O = 75 ∣10∣ = 3 2 = 3 2 3
⇒ (3) false \Rightarrow \text{(3) false} ⇒ (3) false
cos θ = ∣ ( 7 , − 5 , 1 ) ⋅ ( 2 , 2 , 1 ) ∣ 75 ⋅ 3 = 5 15 3 = 1 3 3 \cos\theta = \dfrac{|(7,-5,1)\cdot(2,2,1)|}{\sqrt{75}\cdot 3} = \dfrac{5}{15\sqrt3} = \dfrac{1}{3\sqrt3} cos θ = 75 ⋅ 3 ∣ ( 7 , − 5 , 1 ) ⋅ ( 2 , 2 , 1 ) ∣ = 15 3 5 = 3 3 1
⇒ (4) TRUE \Rightarrow \text{(4) TRUE} ⇒ (4) TRUE
True: ( 1 ) and ( 4 ) \text{True: } (1)\ \text{and}\ (4) True: ( 1 ) and ( 4 )
( 1 ) and ( 4 ) \boxed{(1)\ \text{and}\ (4)} ( 1 ) and ( 4 )