TS EAMCET · Maths · Properties of Triangles
\(\begin{aligned} & \text { In } \quad \Delta A B C \text {, } \ & a\left(\cos ^2 B+\cos ^2 C\right)+\cos A(c \cos C+b \cos B) \text { is } \ & \text { equal to }\end{aligned}\)
- A a
- B b
- C c
- D a+b+c
Answer & Solution
Correct Answer
(A) a
Step-by-step Solution
Detailed explanation
\begin{aligned} & a\left(\cos ^2 B+\cos ^2 C\right)+\cos A(c \cos C+b \cos B) \\ & =a\left[\left(\frac{a^2+c^2-b^2}{2 a c}\right)+\left(\frac{a^2+b^2-c^2}{2 a b}\right)\right] \\ & +\frac{b^2+c^2-a^2}{2 b c}\left[c\left(\frac{b^2+a^2-c^2}{2 a…
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