The diagram shows the side view of a 14 cm14\text{ cm} by 8 cm8\text{ cm} rectangular block PQRSPQRS, placed on a ramp, VSVS, tilted at an acute angle of θ∘\theta^\circ.
The ramp is placed on a horizontal surface STST and dd is the perpendicular distance from QQ to STST. ∠VTS=90∘\angle VTS = 90^\circ.

  1. (a)

    Show that d=8cos⁡θ+14sin⁡θd = 8\cos\theta + 14\sin\theta.

  2. (b)

    Express dd in the form Rcos⁡(θ−α)R\cos(\theta - \alpha), where R>0R > 0 and 0∘<α<90∘0^\circ < \alpha < 90^\circ.

  3. (c)

    Find the smallest value of θ\theta such that d=102d = 10\sqrt{2}.

Work through it with AI →

It won't just hand you the answer — it asks where you're stuck.How the checker works

Worked solution

10(a)

1. Identify the relevant right-angled triangles to express the vertical distance $d$.

Let the vertical line from QQ meet the horizontal line through RR at AA, and let the vertical line from RR meet STST at BB. Then d=QA+RBd = QA + RB.

2. Find the lengths of the segments using trigonometry.

In △RSB\triangle RSB, ∠RSB=θ\angle RSB = \theta. Since RS=PQ=14RS = PQ = 14, RB=14sin⁡θRB = 14\sin\theta.
In △QRA\triangle QRA, ∠QRA=90∘−∠ARS=90∘−(90∘−θ)=θ\angle QRA = 90^\circ - \angle ARS = 90^\circ - (90^\circ - \theta) = \theta.
Since QR=8QR = 8, QA=8cos⁡θQA = 8\cos\theta.
Therefore, d=QA+RB=8cos⁡θ+14sin⁡θd = QA + RB = 8\cos\theta + 14\sin\theta.

Answer

Shown

10(b)

1. Expand the target form and compare coefficients with the given expression

Rcos⁡(θ−α)=Rcos⁡θcos⁡α+Rsin⁡θsin⁡αR\cos(\theta - \alpha) = R\cos\theta\cos\alpha + R\sin\theta\sin\alpha
Comparing with 8cos⁡θ+14sin⁡θ8\cos\theta + 14\sin\theta:
Rcos⁡α=8R\cos\alpha = 8
Rsin⁡α=14R\sin\alpha = 14

2. Calculate the value of R

R=82+142R = \sqrt{8^2 + 14^2}
R=64+196=260=265≈16.1245R = \sqrt{64 + 196} = \sqrt{260} = 2\sqrt{65} \approx 16.1245

3. Calculate the value of alpha

tan⁡α=148=1.75\tan\alpha = \frac{14}{8} = 1.75
α=tan⁡−1(1.75)≈60.255∘\alpha = \tan^{-1}(1.75) \approx 60.255^\circ

4. State the final expression

d=260cos⁡(θ−60.3∘)d = \sqrt{260}\cos(\theta - 60.3^\circ)

Answer

260cos⁡(θ−60.3∘)\sqrt{260}\cos(\theta - 60.3^\circ) or 16.1cos⁡(θ−60.3∘)16.1\cos(\theta - 60.3^\circ)

10(c)

1. Recall or calculate the values of $R$ and $\alpha$ from part (b)

From part (b), d=Rcos⁡(θ−α)d = R\cos(\theta - \alpha).
R=82+142=260R = \sqrt{8^2 + 14^2} = \sqrt{260}
tan⁡α=148  ⟹  α=tan⁡−1(1.75)≈60.255∘\tan\alpha = \frac{14}{8} \implies \alpha = \tan^{-1}(1.75) \approx 60.255^\circ
So, d=260cos⁡(θ−60.255∘)d = \sqrt{260}\cos(\theta - 60.255^\circ)

2. Set up the equation with the given value of $d$

260cos⁡(θ−60.255∘)=102\sqrt{260}\cos(\theta - 60.255^\circ) = 10\sqrt{2}

3. Isolate the cosine term and find the basic angle

cos⁡(θ−60.255∘)=102260=200260=1013\cos(\theta - 60.255^\circ) = \frac{10\sqrt{2}}{\sqrt{260}} = \sqrt{\frac{200}{260}} = \sqrt{\frac{10}{13}}
Basic angle =cos⁡−1(1013)≈28.716∘= \cos^{-1}\left(\sqrt{\frac{10}{13}}\right) \approx 28.716^\circ

4. Solve for the smallest positive value of $\theta$

θ−60.255∘=−28.716∘ or 28.716∘\theta - 60.255^\circ = -28.716^\circ \text{ or } 28.716^\circ
θ=60.255∘−28.716∘=31.539∘ or θ=60.255∘+28.716∘=88.971∘\theta = 60.255^\circ - 28.716^\circ = 31.539^\circ \text{ or } \theta = 60.255^\circ + 28.716^\circ = 88.971^\circ
The smallest value of θ\theta is 31.5∘31.5^\circ (to 1 d.p.).

Answer

31.5∘31.5^\circ

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

  1. 1Solve the equation 2cot⁡22x=1−5sin⁡2x2 \cot^2 2x = 1 - \frac{5}{\sin 2x} for −180∘≤x≤180∘-180^\circ \le x \le 180^\circ.
  2. 2已知sin⁡(α+π12)=55\sin (α+ \dfrac {π}{12} )= \dfrac { \sqrt {5}}{5},则sin⁡(π3−2α)=(    )\sin ( \dfrac {π}{3} -2α)= (\:\:\:\:) A. 45 \dfrac {4}{5}…
  3. 38.8.设△ABC\triangle ABC的内角AA,BB,CC所对的边分别为aa,bb,cc,若bcos⁡C+ccos⁡B=asin⁡Ab\cos C+c\cos B=a\sin A,则△ABC\triangle ABC的形状为…
  4. 4Prove that sin⁡3xsec⁡2x+sin⁡x=tan⁡xsec⁡x\sin^{3} x\sec^{2} x + \sin x = \tan x\sec x. Solve the equation sin⁡3xsec⁡2x+sin⁡x=5\sin^{3} x\sec^{2} x + \sin x = 5 for 0≤x≤360∘0 \le x \le 360^\circ…
  5. 5Given that cos⁡x=−45\cos x = -\frac{4}{5} and tan⁡x>0\tan x > 0, find sin⁡2x\sin 2x, cos⁡x2\cos \frac{x}{2}.