5 · 5 - 4 · 4 = 9 sorry if I'm wrong
the dots mean to multiply
Answer:
1/sqrt10
Step-by-step explanation:
1) Find out cosA using formula (cosA)^2+(sinA)^2=1
The module of cosA= sqrt (1- (-3/5)^2)= sqrt 16/25=4/5
So cosA=-4/5 or cosA=4/5.
Due to the condition 270degrees< A<360 degrees, 0<cosA<1 that's why cosA=4/5.
2) Find sinA/2 using a formula cosA= 1-2sinA/2*sinA/2 where cosA=4/5.
(sinA/2)^2= 0.1
sinA= sqrt 0.1= 1/ sqrt10 or sinA= - sqrt 0.1= -1/sqrt10
But 270°< A< 360°, then 270/2°<A/2<360/2°
135°<A/2<180°, so sinA/2 must be positive and the only correct answer is
sin A/2= 1/sqrt10
The 31st term of this sequence is 189.
9, 15, 21, 27, 33 (5), 39, 45, 51, 57, 63 (10), 69, 75, 81, 87, 93 (15), 99, 105, 111, 117, 123 (20), 129, 135, 141, 147, 153 (25), 159, 165, 171, 177, 183 (30), 189.
