In a right triangle, the acute angles have the relationship

sin(x + 12°) = cos(18° + 2x). What is the value of x? What is the measure of the smaller angle? Use 1-2 sentences to explain how you arrived at your answers.
(2 points)

3 answers

To solve the equation \( \sin(x + 12°) = \cos(18° + 2x) \), we utilize the identity \( \cos(θ) = \sin(90° - θ) \). Rewriting the equation gives us:

\[ \sin(x + 12°) = \sin(90° - (18° + 2x)) \]

This simplifies to:

\[ \sin(x + 12°) = \sin(72° - 2x) \]

Setting the arguments equal to each other leads to two equations. The first gives us:

\[ x + 12° = 72° - 2x \]

Solving this, we find:

\[ 3x = 60° \] \[ x = 20° \]

The second sine equation could lead to a different solution, but in this case, the values produced would not yield a valid angle when considering the constraints of a right triangle and the given equation.

For the measure of the smaller angle in the triangle, we have \( x = 20° \) and the other acute angle would be \( 90° - 20° = 70° \). Thus, the measure of the smaller angle is \( 20° \).

In summary, I set the equations from the given trigonometric identity, solved for \( x \), and determined the smaller angle from the right triangle's properties. The answers are \( x = 20° \) and the smaller angle is \( 20° \).

Can u make this copy and pasteable

Sure! Here is the solution in a copy-pasteable format:


To solve the equation \( \sin(x + 12°) = \cos(18° + 2x) \), we utilize the identity \( \cos(θ) = \sin(90° - θ) \). Rewriting the equation gives us:

\[ \sin(x + 12°) = \sin(90° - (18° + 2x)) \]

This simplifies to:

\[ \sin(x + 12°) = \sin(72° - 2x) \]

Setting the arguments equal to each other leads to two equations. The first gives us:

\[ x + 12° = 72° - 2x \]

Solving this, we find:

\[ 3x = 60° \] \[ x = 20° \]

The second sine equation could lead to a different solution, but in this case, the values produced would not yield a valid angle when considering the constraints of a right triangle and the given equation.

For the measure of the smaller angle in the triangle, we have \( x = 20° \) and the other acute angle would be \( 90° - 20° = 70° \). Thus, the measure of the smaller angle is \( 20° \).

In summary, I set the equations from the given trigonometric identity, solved for \( x \), and determined the smaller angle from the right triangle's properties. The answers are \( x = 20° \) and the smaller angle is \( 20° \).


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