Angles-In-Triangle Wjec-Eduqas Foundation

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Exam code:C300

Angles in triangles

What are the angle properties of triangles?

The three interior angles inside any triangle add up to 180°
If the triangle is isosceles then two angles will be equal
- These will be the two angles opposite the two sides of equal length
If the triangle is equilateral then all three angles will be equal
- Each angle will equal 60°

A right-angled triangle has one 90° angle

Examiner Tips and Tricks

Find all the missing angles that you can using the angles that are given to you in a question
- They might not seem to help you straight away but having more angles will lead you to find the angle you need

Worked Example

The diagram below is formed using three straight lines. Find the value of $x$ .

Label the other missing angles inside the triangle

Triangle angle properties worked example working

Vertically opposite angles between two intersecting lines are equal

$y space equals space 60$

Angles that meet on a straight line add up to 180°

$table row cell z space plus space 130 space end cell equals cell space 180 space end cell row cell z space end cell equals cell space 50 end cell end table$

Interior angles in a triangle add up to 180°

<img alt=”table row cell x plus 60 plus 50 end cell equals 180 row cell x plus 110 end cell equals 180 end table” data-mathml=”<math ><semantics><mtable columnspacing=”0px” columnalign=”right center left”><mtr><mtd><mi>x</mi><mo>+</mo><mn>60</mn><mo>+</mo><mn>50</mn></mtd><mtd><mo>=</mo></mtd><mtd><mn>180</mn></mtd></mtr><mtr><mtd><mi>x</mi><mo>+</mo><mn>110</mn></mtd><mtd><mo>=</mo></mtd><mtd><mn>180</mn></mtd></mtr></mtable><annotation encoding=”application/vnd.wiris.mtweb-params+json”>{“fontFamily”:”Times New Roman”,”fontSize”:”18″,”autoformat”:true,”toolbar”:”<toolbar ref=’general’><tab ref=’general’><removeItem ref=’setColor’/><removeItem ref=’bold’/><removeItem ref=’italic’/><removeItem ref=’autoItalic’/><removeItem ref=’setUnicode’/><removeItem ref=’mtext’ /><removeItem ref=’rtl’/><removeItem ref=’forceLigature’/><removeItem ref=’setFontFamily’ /><removeItem ref=’setFontSize’/></tab></toolbar>”}</annotation></semantics></math>” data-type=”working” height=”48″ role=”math” src=”data:image/svg+xml;charset=utf8,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20xmlns%3Awrs%3D%22http%3A%2F%2Fwww.wiris.com%2Fxml%2Fmathml-extension%22%20height%3D%2248%22%20width%3D%22125%22%20wrs%3Abaseline%3D%2223%22%3E%3C!–MathML%3A%20%3Cmath%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmtable%20columnalign%3D%22right%20center%20left%22%20columnspacing%3D%220px%22%3E%3Cmtr%3E%3Cmtd%3E%3Cmi%3Ex%3C%2Fmi%3E%3Cmo%3E%2B%3C%2Fmo%3E%3Cmn%3E60%3C%2Fmn%3E%3Cmo%3E%2B%3C%2Fmo%3E%3Cmn%3E50%3C%2Fmn%3E%3C%2Fmtd%3E%3Cmtd%3E%3Cmo%3E%3D%3C%2Fmo%3E%3C%2Fmtd%3E%3Cmtd%3E%3Cmn%3E180

Maths Gcse Wjec-Eduqas Foundation

Angles-In-Triangle Wjec-Eduqas Foundation

Angles in triangles

What are the angle properties of triangles?

Examiner Tips and Tricks

Worked Example

Responses