4MA0 Foundation January 2017 Paper 1R Q19

EdexcelFoundationOld spec4 marks2D Area & Perimeter Pythagoras

19 Here is an isosceles triangle.

Diagram NOT accurately drawn

Work out the area of the triangle.
Give your answer correct to 3 significant figures.

(4)

Mark scheme

M1: or M1 for \(\cos x = \dfrac{7}{18}\) or \(\sin y = \dfrac{7}{18}\)

or \(\cos z = \dfrac{18^2 + 18^2 - 14^2}{2 \times 18 \times 18}\)

M1: or M1 for \(x = \cos^{-1}\left(\dfrac{7}{18}\right)\) or \(x = 67.1\ldots\)

or \(y = \sin^{-1}\left(\dfrac{7}{18}\right)\) or \(y = 22.8\ldots\)

or \(z = \cos^{-1}\left(\dfrac{18^2 + 18^2 - 14^2}{2 \times 18 \times 18}\right)\) or \(z = 45.77\ldots\)

M1: or M1 for 0.5×14×18×sin(“67.1…”) or
0.5×18×18×sin(2×“22.8…”) or
0.5×18×18×sin(“45.77…”)

A1: 116 – 116.1
NB Allow use of Hero’s formula