Question

a) sin A + sin B + sin C
b) cos A + cos B + cos C
c) 3
d) 3 root3/2​

Answer 1

Answer:

Option B is correct

Sorry I cannot explain. I need to sleep. But answer is correct 100%

Answer 2

Answer:

b) cos A + cos B + cos C

Step-by-step explanation:

Sum of three interior angles of a triangle = 180°

A + B + C = 180

=> A = 180 - B - C

=> B = 180 - A - C

=> C = 180 - A - B

Substitute these values in the given expression...

=> sin ( 180-A-C+180-A-B-180+B+C/2) + sin ( 180-A-B + 180-B-C - 180+A+C/2) + sin( 180-B-C + 180-A-C -180+A+B/2)

=> sin (180-2A/2) + sin( 180-2B/2) + sin(180 -2C/2)

=> sin(90-A) + sin(90-B) + sin( 90- C)

=> cosA + cosB + cosC (Complementary angles)

Hope it helps you:)