The diagram shows the front view of a rectangular block , with dimensions 14 cm by 8 cm, placed on a ramp, , tilted at an acute angle of and . The ramp is placed on a horizontal surface and is the perpendicular distance from to .

- (a)
Show that .
- (b)
Express in the form , where and .
- (c)
State the maximum value of and find the corresponding value of .
- (d)
Find the smallest value such that .
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Worked solution
4(a)
1. Identify the horizontal and vertical components of the rectangle's sides by drawing a horizontal line through C and a vertical line from B.
Let be the foot of the perpendicular from to the horizontal line . Let be the foot of the perpendicular from to the horizontal line passing through .
The total vertical distance is the sum of the vertical distance from to (which is ) and the vertical distance from to (which is ).
2. Express the vertical segments in terms of $\theta$ using trigonometry.
In the right-angled triangle , the angle (since lies on the ramp which is inclined at ).
In the right-angled triangle , the angle .
Therefore, .
(shown)
4(b)
1. Identify the form and expand $R \sin(\theta + \alpha)$
2. Find the value of $R$
Comparing coefficients:
3. Find the value of $\alpha$ and write the final expression
(to 1 d.p.)
4(c)
1. State the maximum value of $d$ using the $R$ value from part (b)
From part (b), .
The maximum value of is .
Maximum value of (to 3 s.f.)
2. Find the corresponding value of $\theta$
For maximum ,
(to 1 d.p.)
Maximum value of , corresponding
4(d)
1. Set up the equation using the $R$-formula result from part (b)
From part (b), and .
Equating to 13:
2. Solve for the basic angle
3. Find the smallest positive value of $\theta$
For the smallest value of , we take the first quadrant solution:
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