A triangle has sides of length 8 cm, 10 cm and 14 cm. Work out the size of the largest angle of the triangle. Give your answer correct to 1 decimal place.

Utilising the cosine rule: c² = a² + b² - 2abcosC, substitute in the given lengths. We therefore get that 14² = 10² + 8² − 2 × 10 × 8 × cosA . Expanding this expression we then get that 196 = 164 - 160cosA. Then, rearranging the equation gives us that cosA = -1/5. Inputting this into the calculator gives us that A = 101.5 degrees (to one decimal place). We know that this is the largest angle in the triangle since the sum of the angles in a triangle is 180 degrees. 101.5 > 78.5, therefore the answer is correct.

JK
Answered by Josephine K. Maths tutor

17887 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Each day Chen buys pasta or a sandwich. Where Pasta costs £3.20 and Sandwich costs £2.75. For 45 days, the relative frequency of Chen buying a sandwich was one fifth. Altogether, how much did he pay?


Solve the following simultaneous equation for x and y: 2x + 5y = 8, 4x + y = 7


Solve the Simultaneous Equation: 2x + 3y = 15 and 5x + 4y = 13


How do I factorise quadratic equations?


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning