If C D = 3 , P Q = 2 , and ∠ P D Q = 3 0 ∘ , find C P .
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why do you conclude it that it is 1
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from that equation we get 2 roots 1 & -3 distance can not be -3 so the answer is 1...
Because 1 and and -3 is the answer. And in measurements, we must always use a number greater than 0.
Cause length can be only positive. . not negative.. SEE....if take take eq. (x+3), then x will be -3 , agree? and if we take (x-1), x will be 1 and 1 is positive . Hope it helped :D
it is very good!!
What exactly happened to the root3 in the equation there? Literally disappeared. Went from a fraction that simplifies into (x+1)/([1/root3]-x) to suddenly x+2.
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Sorry, I skipped a few steps for sake of expediency. Expanding on the steps, we have
3 x + 2 = 1 − ( 3 x ) ∗ ( 3 1 ) 3 x + 3 1 ⟹ x + 2 = 1 − 3 x 3 ∗ 3 x + 1 ⟹ x + 2 = 3 3 − x x + 1
⟹ ( x + 2 ) ( 3 − x ) = 3 ∗ ( x + 1 ) ⟹ x 2 + 2 x − 3 = 0 ⟹ ( x + 3 ) ( x − 1 ) = 0 .
Let B = CDP and X = CP:
Tan B = X/sqrt(3) Tan (30 + B) = (2 + X)/sqrt(3) By trigo identities; Tan (M +- N) = (Tan M +- Tan N)/(1 -+ Tan M Tan N) Tan 30 = 1/sqrt(3) = sqrt(3)/3 So, (Tan 30 + Tan B)/(1 - Tan 30 Tan B) = (2 + X)/sqrt(3) Subs Tan B = X/sqrt 3 Solving the equation will give X = 1
Consider triangle PDQ. By the law of cosines:
D P 2 + D Q 2 − 2 cos 3 0 ° D P ⋅ P Q = 4
By Pithagoras we have:
D P 2 = C P 2 + 3
and
D Q 2 = ( C P + 2 ) 2 + 3
As for the product of DQ and DP, let us consider the area A of triangle DPQ:
2 A = 2 3 = D Q ⋅ D P ⋅ sin 3 0 °
hence
D P ⋅ D Q = 4 3
Let us substitute in the first equation and solve by CP:
C P 2 + 3 + C P 2 + 2 C P + 4 + 3 − 2 ⋅ 4 3 ⋅ 2 3 = 4
⟺ 2 C P 2 + 2 C P − 6 = 0
⟺ C P 2 + C P − 3 = ( C P + 3 ) ( C P − 1 ) = 0
and since CP cannot be -3, it must be 1.
Let B = CDP and X = CP:
Tan B = X/sqrt(3) Tan (30 + B) = (2 + X)/sqrt(3) By trigo identities; Tan (M +- N) = (Tan M +- Tan N)/(1 -+ Tan M Tan N) Tan 30 = 1/sqrt(3) = sqrt(3)/3 So, (Tan 30 + Tan B)/(1 - Tan 30 Tan B) = (2 + X)/sqrt(3) Subs Tan B = X/sqrt 3 Solving the equation will give X = 1
area of∆ dcq=1\2×(2+R)×√3=area∆ cpd+area ∆pqd=1\2×R×√3+1\2×M×N×sin30,R=cp,M=Dp,N=DQ,OK ,,1\2×(2+R)√3=1\2×R×√3+1\2×M×N×1\2,,,so 2√3+R√3=R√3+M×N×1\2,M×N=4√3,,,,,,,,,,,,,,,, cos30=M^2+N^2-4\2M.N ,√3×M.N=M^2+N^2-4. M×N=4√3 ,so 4√3×√3=M^2+48\M^2-4. M^2+48\M^2=16,multiple expression by M^2. M^4-16M^2+48=0.(m^2-12).(m^2-4)=0 so m^2=12 Or 4 , m^2. N^2=48 so ,N^2=48\12=4 . N=2 rejected N>PQ>2.,,,so M^2=2 , . R^2=2^2-√3^2=1.R=1=CP###########
Length of PQ=length of PD By using Pythagora's thm PD^{2}=DC^{2}+CP^{2} thus to get the length of CP, CP=\sqrt{2^2-3} so CP=1
triangle DCP is a special triangle... a 30-60-90 triangle whose sides are always x-x*3^1/2-2x... once you see that the question pretty much solves itself.
Where do get that the triangle is 30-60-90? I assumed it to get the answer, but nowhere does it say that segment D P bisects angle C D Q , that D P = P Q , or that D Q = 2 ∗ 3
put, CP=X, area of CDQ(1/2 x root 3 x X+2) = area CDP(1/2 x root 3 x X)+ area DPQ ( 1/2 x sin 30 x DP x DQ)...........(1)
here, DP = root (3+x^2) and DQ = root(3+ (X+2)^2) solve eqn (1), the possible value of it comes 1, hence CP=1
triangle DPQ having base-2 m and perpendicular height-root3 .then
tan 30=(2+x)/root3;
1/root3=(2+x)/root3;
2+x=1.
hence x=-1(where x is length of CP)
solength of CP=1
Triangle DCQ is a 30-60-90 triangle since angle CDQ = 60 and angle C = 90. Since angle Q = 30, triangle PDQ is isosceles which tells us that DP = 2m. Now use the Pythagorean theorem on triangle CDP to find CP: CD^2+CP^2=DP^2 3 + CP^2 = 4
which tells us CP = 1
Triangle DCQ is a 30-60-90 triangle since angle CDQ = 60 and angle C = 90. Since angle Q = 30, triangle PDQ is isosceles which tells us that DP = 2m. Now use the Pythagorean theorem on triangle CDP to find CP:
3 + CP^2 = 4
which tells us CP = 1
How did you figure out that triangle dcq is a 30-60-90 triangle? ??
Of course there's a rigorous method to find the length but here's what i did- i randomly chose the value of angle CPD, first 30 but that means CDQ is 90 that's absurd. Then i put CPD=60, that means CQD=30=>DP=PQ=2 & CP=1 & i checked this combination using Pythagoras and it worked!! Pretty much saved my time.
I made system with , Pitagora' s theorem , Stweart's theorem and law of cosine, solve it to find DQ , CP and DP
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Let ∠ C D P = θ and C P = x .
Then tan ( θ ) = 3 x and tan ( θ + 3 0 ) = 3 x + 2 .
Now tan ( θ + 3 0 ) = 1 − tan ( θ ) ∗ tan ( 3 0 ) tan ( θ ) + tan ( 3 0 ) , so
3 x + 2 = 1 − ( 3 x ) ∗ ( 3 1 ) 3 x + 3 1 ⟹ x + 2 = 1 − 3 x x + 1
⟹ ( x + 2 ) ( 3 − x ) = 3 ∗ ( x + 1 ) ⟹ x 2 + 2 x − 3 = 0 ⟹ ( x + 3 ) ( x − 1 ) = 0 .
Now since we require that x > 0 we conclude that x = 1 .