Question

URGENT ANSWER NOW In △ABC, A=59∘, a=20, and c=21. What are the two possible values for angle C to the nearest tenth of a degree? Select both correct answers.

Select all that apply:

C=111.8∘
C=115.8∘
C=66.2∘
C=113.8∘
C=68.2∘
C=64.2∘

Answer 1

The two possible values of C are 64.2° and 115.8°

Explanation:

* In ΔABC

- a, b, c are the lengths of its 3 sides, where

# a is opposite to angle A

# b is opposite to angle B

# c is opposite to angle C

- m∠A = 59°

- a = 20

- c = 21

* To find the distance m∠C we can use the sin Rule

- In any triangle the ratio between the length of each side

to the measure of each opposite angle are equal

- c/sinC = a/sinA = b/sinB

* Lets use it to find the m∠C

∵ 21/sinC = 20/sin(59)

∴ sin(C) = 21 × sin(59) ÷ 20 = 0.9000256657

∴ m∠C = sin^-1(0.9000256657) = 64.16144°

∴ m∠C = 64.2°

∵ The value of sin(C) is positive

∴ Angle C may be in the first quadrant (acute angle)

or in the second quadrant (obtuse angle)

∴ The other measure of ∠C = 180 - 64.2 = 115.8

* The two possible values of C are 64.2° and 115.8°