Question

Suppose a triangle has sides a, b, and c, and that a2 + b2 < c2. Let be the measure of the angle opposite the side of length c. Which of the following must be true? Check all that apply.

Answer 1

\[A. cos \theta\] <0
B. the triangle is a right triangle
C. the triangle is not a right triangle
\[D. \theta \] is an obtuse angle

help me please

Answer 2

I don't know

Answer 3

http://mathworld.wolfram.com/ObtuseTriangle.html

Answer 4

I need more help I do not understand

Answer 5

use the cosine rule

Answer 6

cos C = (a^2 + b^2 - c^2)/(2ab)
we knowed that a^2 + b^2 < c^2
obviously, the numerator be negative and the denominator is positive.
cos C = -/+
cos C = -
so, <C is in the 2nd quadrant (more than 90 degrees)
finally, it is an obtuse triangle

Answer 7

so the answer is only D

Answer 8

wait, is the theta the measure of the angle opposite the side of length c ?

Answer 9

check the original question....
let .?..
(is it theta)

Answer 10

you see the picture

Answer 11

aha, i thought that is the theta :)
you just miss it after you type let ........

Answer 12

cos C = cos θ
like i said above :
cos C = -
it means that cos θ < 0 (A is correct, and D is correct too)

Answer 13

Suppose a triangle has sides a, b, and c, and that a2 + b2 < c2. Let be the measure of the angle opposite the side of length c. Which of the following must be true? Check all that apply.

A. The triangle is not a right triangle.
B. The triangle is a right triangle.
C. cos < 0
D. is an acute angle.