Question

How do you solve law of cosine?​

Answer 1

Explanation:

Use the Law of Cosines when you know the lengths of two sides, and the angle between them. That is not the case here. You know b=24, c=21, and B=61°, but B is not between b and c.

Use the Law of Sines.

sinC/c = sinB/b

sinC = c×sinB/b

C = arcsin(c×sinB/b)

= arcsin(24sin61°)/21)

≈ 49.9°

A = 180° - B - C ≈ 69.1

a/sinA = b/sinB

a = sinA×b/sinB

= sin(69.1°)×21/sin(61°)

≈ 25.6 units

Answer 2

Draw and label a standard Oblique Triangle, as we’ve done in our previous lessons.

Determine the given congruence, either SAS or SSS, and pick the equation that helps you solve for either a missing side or angle.

Plug into your chosen equation and solve.

The "Law of Cosines" can be used to calculate one side of a triangle when the angle opposite and the other two sides are known. The "Law of Cosines" can be expressed as c2 = a2 + b2 - 2 a b cos C (1)

The cosine rule is an extension of this mathematic principal that makes it effective for non-right triangles and states that in regard to a certain angle, the square of the side of the triangle opposite that angle is equal to the squares of the other two sides added together, minus two times both..