If the cosine of their angle is the root of the equation 5x2-7x-6 = 0, then the length of the other side of the triangle is () A. 52B. 213C. 16D. 4

If the cosine of their angle is the root of the equation 5x2-7x-6 = 0, then the length of the other side of the triangle is () A. 52B. 213C. 16D. 4

By solving the equation 5x2-7x-6 = 0, the root of the equation is 2 or - 35, so the cosine of the angle cos θ = - 35. According to the cosine theorem, the length of the other side of the triangle is 32 + 52 − 2 × 3 × 5 × (− 35) = 213

If both sides of a triangle are 5 and 3, and the cosine of their angle is the root of the equation 5x-7x-6 = 0, then the triangle is

Root of 5x-7x-6 = 0, X1 = - 3 / 5, X2 = - 2 (rounding)
Cosine theorem:
Let the third side be c
-3/5=(5^2+3^2-c^2)/2*3*5
C ^ 2 = 61 C = radical 61

The shadow part is three semicircles with the radius of the three sides of the direct triangle. It is known that the areas of the upper semicircles of the two right angles are 9 / 2 π and 8 π respectively, so it is necessary to calculate the skew
The length of the side

It's three sides in diameter, right
The area of the circle is π R & # 178; = π D & # 178 / 4, R is the radius, D is the diameter
Two right angle sides are brought into the circle area formula respectively
It can be found that the two right angles are 6 and 8 respectively
Then the hypotenuse is 10
1/2×（πa²/4）=9/2π
1/2×（πb²/4）=8π
A = 6, B = 8
So C = 10

In △ ABC, if (a + B + C) (B + C-A) = 3bC and Sina = 2sinbcosc, then the shape of △ ABC is ()
A. Right triangle B. isosceles right triangle C. isosceles triangle D. equilateral triangle

∵ (a + B + C) (B + C-A) = 3bC ∵ [(B + C) + a] [(B + C) - A] = 3bC ∵ (B + C) 2-A2 = 3bcb2 + 2BC + c2-a2 = 3bcb2 BC + C2 = A2 according to the cosine theorem, there are A2 = B2 + c2-2bccosa ∵ B2 BC + C2 = A2 = B2 + c2-2bccosabc = 2bccosacosa = 12 ∵ a = 60 ° Sina = 2sinbcossin (B + C

If (a + B + C) (B + C – a) = 3ABC and Sina = 2sinbcosc, then ABC is a triangle_____

Yeah.. Isn't that the same thing in my answer

In the triangle ABC, if B = 5, angle B = 1 / 4, sin a = 1 / 3, then a =?

According to the sine theorem
a/sinA = b/sinB
a =bsinA/sinB= 5*(1/3)/(sinπ/4) = (5√2)/6

In triangle ABC, a = 60 degrees, B = 1, s triangle ABC = root 3, then a + B + C / Sina + SINB + sinc = 3Q

Area s = 1 / 2 * bcsina, C = 4, cosine theorem a ^ 2 = B ^ 2 + C ^ 2-2bccosa, a = root 13, sine theorem and equal ratio Theorem A / Sina = B / SINB = C / sinc = (a + B + C) / (Sina + SINB + sinc) get (2 * root 39) / 3

In the triangle ABC, if B is equal to 5, angle B is equal to quarter pie, and sin a is equal to one third, then a is equal to?

From the sine theorem a / Sina = B / SINB
A = bsina / SINB = 5 radical 2 / 3

In △ ABC, "a > b" is the establishment of "Sina > SINB" ()
A. Sufficient and necessary condition B. sufficient and necessary condition C. necessary and insufficient condition D. neither sufficient nor necessary condition

If a and B are both acute angles, it is obvious that "Sina > SINB" holds. If one of a and B is an acute angle, it is necessary that B is an acute angle. In this case, π - A is not an obtuse angle. Because a + B < π, there must be B < π - a ≤ π 2. In this case, sin (π - a) = Si

In △ ABC, if edge AB is the largest edge and Sina · SINB = 2-34, then the maximum value of Cosa · CoSb is______ ．

In the ABC of the triangle ABC, AB is the longest, so the angle c is the largest, so the angle c is the largest, so the angle c is the largest, so the angle c is the largest, so \\\\\abcis the longest, so the angle c is the largest, and \\\\\\ (a-b) - cos (a + b) is (a + b) = (2-3, \\\\\\\\\\\\\\\\\\\\\\\\\\\ifand only if a= The answer is: 3 + 24