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.

Answered by Josephine K. Maths tutor

16157 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

The y-intercept of A is 7. A also passes through point (7, 2). (a) Find an equation of A in the form y = mx + c. (b) B is perpendicular to A and also has a y-intercept of 7. Write down the equation for B in the form y = mx + c.


A car costs £5,899.99, not including VAT. If the VAT rate is 20% how much does the car cost in total?


How to multiply and divide mixed fractions


√5( √8 +√18) can be written in the form a√10 where a is an integer.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo
Cookie Preferences