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

17405 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

A linear sequence starts, a + 2b, a + 6b, a + 10b …….. …….. The 2nd term has value 8. The 5th term has value 44. Work out the values of a and b


How can you expand brackets? e.g: (x-4)(x+7)


√3(√30 + √8) can be simplified into the follwing format: x√10 + y√6 where are x and y are integers. Find the value of x and y.


Nadia has £5 to buy pencils and rulers. Pencils are 8p each. Rulers are 30p each. She says “I will buy 15 pencils. Then I will buy as many rulers as possible. With my change I will buy more pencils.” How many pencils and how many rulers does she buy?


We're here to help

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

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences