Question

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

Answer 1

M∠B = 97 degrees

Explanation:

Answer 2

m∠B =
`97^(o)`.

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 =
`(-16800)/(132000)`

= -0.1273

B =
`Cos^(-1)` -0.1273

=
`97^(o)`

Thus, measure of ∠B is
`97^(o)`.