The diagram shows the side view of a 14 cm by 8 cm rectangular block , placed on a ramp, , tilted at an acute angle of .
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)
Find the smallest value of such that .
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Worked solution
10(a)
1. Construct horizontal and vertical lines to form right-angled triangles
Let be the projection of onto the horizontal line . Let be the projection of onto the horizontal line passing through . Then .
2. Express the vertical components in terms of $\theta$
In , . Since cm, .
In , (since is perpendicular to and is parallel to ). Since cm, .
Therefore, .
Shown
10(b)
1. Expand the target form $R\cos(\theta - \alpha)$
2. Equate coefficients with the expression for $d$
From part (a), .
Comparing coefficients:
3. Calculate the value of $R$
4. Calculate the value of $\alpha$
(to 1 d.p.)
So,
10(c)
1. Recall the result from part (b) and set up the equation
From part (b), .
Equating this to :
2. Isolate the cosine term
3. Find the possible values for the angle
4. Solve for the smallest positive value of theta
For the smallest , we take the negative value:
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