Help me plz will mark brainliest

a) pentagon

b) concave

c) not regular

Step-by-step explanation:

a) this polygon has 5 sides, known as a pentagon

b) it is concave because you can connect the top two vertices with a diagonal which will be outside the shape

c) a regular polygon is equilateral (all sides equal) but the markings show that is not the case with this shape

hope it you

step-by-step explanation:

sin(7pi/6 - pi/3)  

= sin(7pi/6 - 2pi/6)  

= sin(5pi/6)  

= sin(pi - pi/6)  

= sin(pi/6)  

= 1/2  

sin 7pi/6 - sin pi/3  

= sin (pi + pi/6) - sin pi/3  

= -sin pi/6 - sin pi/3  

= -1/2 - sqrt(3)/2  

= -(1+sqrt(3))2