Right Triangles: Practice
Question 1 of 5

Select the correct answer.

What is the value of [tex]$x$[/tex] to the nearest tenth?

[tex]\cos (50 + x)^{\circ} = \sin (2x - 6)^{\circ}[/tex]

A. 15.3
B. 46
C. 18.7
D. 44



Answer :

To solve the equation [tex]\(\cos(50 + x)^\circ = \sin(2x - 6)^\circ\)[/tex], we can use trigonometric identities to simplify and solve for [tex]\(x\)[/tex].

First, recall the identity:
[tex]\[ \sin(\theta) = \cos(90^\circ - \theta) \][/tex]

Using this identity, we can rewrite the right-hand side of the given equation:
[tex]\[ \sin(2x - 6)^\circ = \cos(90^\circ - (2x - 6)^\circ) = \cos(96^\circ - 2x) \][/tex]

Now the equation becomes:
[tex]\[ \cos(50 + x)^\circ = \cos(96 - 2x)^\circ \][/tex]

For [tex]\(\cos(A) = \cos(B)\)[/tex], we have two cases to consider:
1. [tex]\(A = B \)[/tex]
2. [tex]\(A = 360^\circ - B\)[/tex]

Applying these to our problem:
### Case 1: [tex]\(50 + x = 96 - 2x\)[/tex]
Solve for [tex]\(x\)[/tex]:
[tex]\[ 50 + x = 96 - 2x \][/tex]
Combine like terms:
[tex]\[ 50 + x + 2x = 96 \][/tex]
[tex]\[ 50 + 3x = 96 \][/tex]
Subtract 50 from both sides:
[tex]\[ 3x = 46 \][/tex]
Divide by 3:
[tex]\[ x = \frac{46}{3} \approx 15.3 \][/tex]

### Case 2: [tex]\(50 + x = 360^\circ - (96 - 2x)\)[/tex]
Simplify the right-hand side:
[tex]\[ 50 + x = 360^\circ - 96 + 2x \][/tex]
[tex]\[ 50 + x = 264 + 2x \][/tex]
Bring [tex]\(x\)[/tex] on one side:
[tex]\[ 50 = 264 + x \][/tex]
Subtract 264 from both sides:
[tex]\[ -214 = x \][/tex]
Which is not a valid solution within the context.

Since only [tex]\(x = 15.3\)[/tex] makes sense, the nearest tenth value we get is:
[tex]\[ \boxed{15.3} \][/tex]

Thus, the correct answer is [tex]\(15.3\)[/tex].