Problem

Problem

In △ABC\triangle ABC , let a=5a = 5 , b=4b = 4 and cos⁡(A−B)=3132\cos(A - B) = \frac{31}{32} , then which of the following statement(s) is (are) correct? a. The perimeter of △ABC\triangle ABC equals 152\frac{15}{2} b. The radius of circle inscribed in △ABC\triangle ABC equals 72\frac{\sqrt{7}}{2} c. The measure of ∠C\angle C equals cos⁡−118\cos^{-1} \frac{1}{8} d. The value of R(b2sin⁡2C+c2sin⁡2B)R(b^2 \sin 2C + c^2 \sin 2B) equals 120

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