高中数学必修四模拟测试题，求答案，急

Question

如题所述

Answer 1

（1）cos(a) = 2sin(a), tan(a) = 1/2.

(2) 12/5 = sin(a)cos(a) + 2,
sin(2a) = 2sin(a)cos(a) = 24/5 - 4 = 4/5.
0 < a < PI/4,
0 < 2a < PI/2. cos(2a) >0,
cos(2a) = 3/5.

sin(2a + PI/4) =sin(2a)cos(PI/4) + cos(2a)sin(PI/4) = (4/5)[1/2^(1/2)] + (3/5)[1/2^(1/2)]
= (7/5)[1/2^(1/2)]
= 7*2^(1/2)/10

Answer 2

1：1/2，2：7根号2/10追问

过程

Answer 3

好好学习……追问

求答案

追答

早就还给老师了