In △ ABC, B & # 178; = A & # 178; + C & # 178; - AC, then the value of B is

In △ ABC, B & # 178; = A & # 178; + C & # 178; - AC, then the value of B is

cosB=(a²+c²-b²)/2ac=ac/2ac=1/2
So B = π / 3

In △ ABC, a, B and C are the opposite sides of ∠ a, B and C, and satisfy a & # 178; + C & # 178; - B & # 178; = AC
Let m vector = (Sina, cos2a), n vector = (- 6, - 1), and find the minimum value of M vector · n vector

CoSb = (A & # 178; + C & # 178; - B & # 178;) / (2Ac) = 1 / 2, then B = 60 degree
W=m*n=－6sinA－cos2A
=2sin²A－6sinA－1
=2[sinA－(3/2)]²－(7/2)
Because 0 degree

In ABC, if B = 60 °, then a & # 178; - AC + C & # 178; - B & # 178=

b²=a²+c²-2accosB
=a²+c²-2accos60°
=a²+c²-1/2x2ac
=a²+c²-ac
So a & # 178; - AC + C & # 178; - B & # 178; = 0
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In △ ABC, ∠ a = 2 ∠ B = 3 ∠ C, then what is the smallest angle in the triangle?

In ∵ △ ABC, ∵ a = 2 ∵ B = 3 ∵ C, ∵ suppose ∵ a = x, then ∵ B = X2, ∵ C = X3. Then x + x2 + X3 = 180 ° and the solution is x = (108011) °, so ∵ C = 108011 °× 13 = 36011 °

In the triangle ABC, c * cosa = B, find the angle C

b/sinB=c/sinC=k
c*cosA=b
ksinC*cosA=ksinB
[sin(C+A)+sin(C-A)]/2=sinB
sin(C-A)=sinB
C-A=B
C=A+B
A+B+C=180
C=90

Let a, B and C be the three sides of △ ABC, and try to explain that a2-b2-c2-2bc is less than 0

A2-b2-c2-2bc = a2 - (B + C) 2 = (a + B + C) (a-b-c), according to the meaning of the title, we can know that: a + B + C > 0, a-b-c < 0, so (a + B + C) (a-b-c) < 0, that is a2-b2-c2-2bc < 0

If a, B and C are the three sides of the triangle ABC, and the square of 3 (a + B + C) = (a + B + C), judge the shape of the triangle ABC

3(a²+b²+c²)=(a+b+c)²3a²+3b²+3c²=a²+b²+c²+2ab+2bc+2ca2a²+2b²+2c²-2ab-2bc-2ca=0(a²-2ab+b²)+(b²-2bc+c²)+(c²-2ac+a...

It is known that a, B and C are the three sides of the triangle ABC and satisfy the square of 3 (the square of a + the square of B + the square of C) = (a + B + C). Try to judge the shape of the triangle ABC

When the two sides are combined, it can be reduced to the square of (a-b) + (B-C) + (A-C) = 0
So there's a = B, B = C, a = C, so it's an equilateral triangle

In triangle ABC, if angle B + angle c = 2, angle a, angle B - angle c = 40 °, then angle a =?, angle B =?, angle c =

∠B+∠C=180°-∠A=2∠A
∠A=60°
∠B+∠C=120°
∠B-∠C=40°
2∠B=160°
∠B=80°
∠C=180°-∠B-∠A=40°

What's the size of a 5-inch, 6-inch, 7-inch, 8-inch photo

5 "12.7 * 8.9 cm
6 "15.2 * 10.2 cm (aspect ratio 3:2)
7 "17.8 * 12.7 cm
8 "20.3 * 15.2 cm (aspect ratio 4:3)
10 inch 25.4 * 20.3cm