Edexcel IGCSE Math A 4.1.D isosceles equilateral right triangles

Practise special-triangle questions by using equal sides to match base angles and combining those facts with line or quadrilateral angles.

Exam points

Use equal sides in an isosceles triangle to identify equal base angles.
Combine right-angle, equilateral or isosceles facts with straight-line angles.
Calculate unknown angles in diagrams containing triangles and quadrilaterals.

[Maximum number: 4]

The diagram shows the triangle PQR.

Diagram NOT accurately drawn

In the diagram, all the angles are in degrees.
R P=R Q
Find the value of y.
Show clear algebraic working.

3x+10=x+522x=42x=21y=180-2(21+52)=34

Final answer:
$34^\circ$

M1 for equating the expressions for angles P and Q.
M1 for isolating the terms in x.
M1 for a complete method.
A1 dependent on M2.

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4.1.D The terms ‘isosceles’, ‘equilateral’ and ‘right-angled question 1