Use the formula for the sum of the first n terms of a geometric sequence to solve. find the sum of the first four terms of the geometric sequence: 2, 10, 50, . . a) 19 b) 312 c) 62 d) 156

The 1st 4 numbers in this sequence will be 2,10,50,250 as the common multiplier=5

So sum of all 4 numbers will be=2+10+50+250=312 (Answer)

answer: cos [   arcsin (3/5) - arccos (1/2) ] =

step-by-step explanation: × = 3/5 = 0.6--> x = 36.87 and x = 180 - 36.87 = 143.13 deg

cos y = 1/2 --> y = +- 60 deg a. cos (x - y) = cos (143.13 - 60) = cos 83,13  

=

0.12

b. cos (36.87 - 60) = cos (-23.23) = 0.92