Pre-U Pre-U 9794/2 2019 Specimen — Question 2 5 marks

Exam BoardPre-U
ModulePre-U 9794/2 (Pre-U Mathematics Paper 2)
Year2019
SessionSpecimen
Marks5
TopicSine and Cosine Rules
TypeGiven area find angle/side
DifficultyModerate -0.5 This is a straightforward application of the triangle area formula (1/2)ab sin C with one equation to solve. Given area = 12, angle C = 30°, and two sides in terms of x, students substitute into 12 = (1/2)(x)(x+2)sin(30°), leading to a simple quadratic equation. While it requires careful algebraic manipulation, it's a standard textbook exercise with no conceptual challenges beyond direct formula application.
Spec1.05c Area of triangle: using 1/2 ab sin(C)

2 \includegraphics[max width=\textwidth, alt={}, center]{48b63de9-f022-4881-a187-f08e3c7d9f1a-2_399_940_952_561} The diagram shows a triangle \(A B C\) in which angle \(C = 30 ^ { \circ } , B C = x \mathrm {~cm}\) and \(A C = ( x + 2 ) \mathrm { cm }\). Given that the area of triangle \(A B C\) is \(12 \mathrm {~cm} ^ { 2 }\), calculate the value of \(x\).

\(\frac{1}{2}x(x+2)\sin 30° = 12\) or simplified expression — B1
Rearrange to get a quadratic equation including putting \(\sin 30° = \frac{1}{2}\) — M1
Obtain \(x^2 + 2x - 48 = 0\) — A1
Solve their quadratic equation — M1
Obtain \(x = 6\) only — A1 [5]
$\frac{1}{2}x(x+2)\sin 30° = 12$ or simplified expression — **B1**
Rearrange to get a quadratic equation including putting $\sin 30° = \frac{1}{2}$ — **M1**
Obtain $x^2 + 2x - 48 = 0$ — **A1**
Solve their quadratic equation — **M1**
Obtain $x = 6$ only — **A1** [5]
2\\
\includegraphics[max width=\textwidth, alt={}, center]{48b63de9-f022-4881-a187-f08e3c7d9f1a-2_399_940_952_561}

The diagram shows a triangle $A B C$ in which angle $C = 30 ^ { \circ } , B C = x \mathrm {~cm}$ and $A C = ( x + 2 ) \mathrm { cm }$. Given that the area of triangle $A B C$ is $12 \mathrm {~cm} ^ { 2 }$, calculate the value of $x$.

\hfill \mbox{\textit{Pre-U Pre-U 9794/2 2019 Q2 [5]}}