Question

Triangle DEF has side lengths e=9 and f=13. If the measure of angle D is 41°, what is the length of side d?

• 13.5
• 5.1
• 6.9
• 8.6

Answer 1

Answer:

8.6

Step-by-step explanation:

Use the law of cosines

$d^{2} = e^{2} + f^{2} -2ef cos D$

$d^{2} = 9^{2} + 13^{2} - 2(9)(13) cos 41\\ = 81 + 169 - 176.602\\ = 73.3979\\d = \sqrt{73.3979} = 8.6$