Respuesta :
An Angle is said to be Acute , if it lies between 0° to 90°.
In terms of Radian
[tex]\rightarrow 0\leq \text{Angle} < \frac{\pi}{2}\\\\ \rightarrow \cos \frac{11\pi }{18}\\\\=\cos(\pi -\frac{7\pi}{18})\\\\=-\cos( \frac{7\pi}{18})[/tex]
⇒Cos(π-A)= -Cos A, becuse cosine of An Angle is Negative in Second Quadrant.
The measure cosine of a positive acute angle is [tex]\rm Cos\dfrac{7\pi }{18}[/tex].
What is the acute angle?
The measure of an angle that is less than 90 degrees (right angle) is called an acute angle.
The cosine function is also equal to;
[tex]\rm Cos(x-\theta)=-Cos\theta[/tex]
Therefore,
The cosine of a positive acute angle. is;
[tex]\rm Cos(\pi -\theta)=-Cos\theta\\\\\theta=\dfrac{11\pi }{18}\\\\\rm =Cos(\pi -\dfrac{11}{18}\pi )\\\\=Cos\dfrac{(18\pi -11\pi }{18})\\\\ =Cos\dfrac{7\pi }{18}[/tex]
Hence, the measure cosine of a positive acute angle is [tex]\rm Cos\dfrac{7\pi }{18}[/tex].
To know more about Acute angle click the link given below.
https://brainly.com/question/2761036
