If the triangle ABC is equal to the triangle def, the circumference of the triangle ABC is 70cm, De is 30cm, DF is 25cm, and the angle B is 25cm
Triangle ABC is equal to triangle def,
The perimeter of triangle ABC is 70cm
So the perimeter of the triangle DEF is 70cm, and the angle B is equal to the angle E
De equals 30cm, DF equals 25cm
So EF equals 15 cm
According to the cosine theorem, the
cosE=(30^2+15^2-25^2)/(2*30*15)=5/9
So angle B = angle e = arccos (5 / 9)
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