Answer:
a = 4.1
Step-by-step explanation:
To find the missing side in the question, we use the cosine rule
That's
Since we are finding a we use the formula
a² = b² + c² - 2(b)(c) cos A
From the question
b = 2
c = 4
A = 78°
Substitute the values into the above formula
We have
a² = 2² + 4² - 2(2)(4) cos 78
a² = 4 + 16 - 16 cos 78
a² = 20 - 16cos 78
a² = 16.67341
Find the square root of both sides
a = 4.0833
We have the final answer as
a = 4.1 to the nearest tenth
Hope this helps you
