Question

In ΔABC, a = 660 cm, b = 680 cm and c=100 cm. Find the measure of ∠B to the nearest degree.

Answer 1

Answer:

M∠B = 97 degrees

Step-by-step explanation:

Answer 2

Answer:

m∠B = $97^{o}$.

Step-by-step explanation:

Since the three sides of the triangle are given, then we apply cosine rule.

$b^{2}$ = $a^{2}$ + $c^{2}$ - 2ac Cos B

But, a = 660 cm, b = 680 cm, and c = 100 cm.

So that;

$680^{2}$ = $660^{2}$ + $100^{2}$ -2(660 x 100) Cos B

462400 = 435600 + 10000 - 132000 Cos B

462400 = 445600 - 132000 Cos B

132000 Cos B = 445600 - 462400

                        = -16800

Cos B = $\frac{-16800}{132000}$

         = -0.1273

B = $Cos^{-1}$ -0.1273

  = $97^{o}$

Thus, measure of ∠B is $97^{o}$.