Use the law of cosines.
a2+b2−2abcosC=c2
Find the measure of angle C. It is the opposite side of c.
c2−a2−b2−2ab=cosC
cosC=13.62−22.52−182−2(22.5)(18)≈0.797
C=cos−10.797=0.649 rad=37.19∘
angle B:
a2+c2−2accosB=b2
cosB=b2−a2−c2−2ac
B=cos−1b2−a2−c2−2ac=cos−1182−22.52−13.62−2(22.5)(13.6)≈0.927 rad=53.13∘
angle A:
b2+c2−2bccosA=a2
A=89.68∘
Answer:
1232
Step-by-step explanation:
213456789
Answer:
The value of angle α is 18 degree.
Step-by-step explanation:
Given information: Angles α and β are the two acute angles , α < β.
Given equation is

![[\because \sin (90-x)=\cos x]](https://tex.z-dn.net/?f=%5B%5Cbecause%20%5Csin%20%2890-x%29%3D%5Ccos%20x%5D)
Equating both sides.




The value of x is 13.
The measure of angles is


Since 18<72, therefore the value of angle α is 18 degree.
Answer:
C
Step-by-step explanation:
See how many pens he has in total from the beginning
21x13 = 273
Then subtract 45 from 273 to see how many he gave up
273-45=228