Question

If A + B + C = 180° then
cos A cos C + cos(A + B) cos(B + C)
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cos A sin C-sin(A + B) cos(B+C)
simplifies to​

Answer 1

Step-by-step explanation:

A+B = 180-C

B+C = 180-A

so question simplifies as:

(cosAcosC + cosCcosA)

___________________

(cosAsinC + sinCcosA)

which can be simplified to,

(2cosAcosC)/(2cosAsinC) = cotC

Answer 2

Step-by-step explanation:

A + B + C = 180° then

cos A cos C + cos(A + B) cos(B + C)

------------------------------------------------

cos A sin C-sin(A + B) cos(B+C)

simplifies to