## Ask Singapore Homework?

Upload a photo of a Singapore homework and someone will email you the solution for free.

## Question

secondary 3 | A Maths

** 2 Answers Below **

Anyone can contribute an answer, even non-tutors.

**Answer This Question**

can someone pls help me solve these 3 equations I can’t seem to get the correct answer

40 • sin² x + 40 • cos² x

= 35 • sin² x - 54 • sin x • cos x

5 • sin² x + 54 • sin x • cos x + 40 • cos² x = 0

(sin x+10cos x) • (5sin x+4cos x) = 0

sin x + 10cos x = 0

tan x = -10

x = 275.71°+360° = 635.71°

5sin x + 4cos x = 0

tan x = -0.8

x = 321.34° + 360° = 681.34°

sin² x - 2•sin x•cos x + cos² x = 0

(sin x - cos x)² = 0

sin x = cos x

x₁ = 45°+360° = 405°

x₂ = 225° ✘

9 - 19 cos 2x + 2• cos ² 2x = 0

(2•cos 2x - 1)•(cos 2x - 9) = 0

2•cos 2x - 1 = 0

cos 2x = 0.5

x= 30° （Answer）

cos 2x - 9 = 0

cos 2x = 9 ✘

### See 2 Answers

*done*{{ upvoteCount }} Upvotes

*clear*{{ downvoteCount * -1 }} Downvotes

*done*{{ upvoteCount }} Upvotes

*clear*{{ downvoteCount * -1 }} Downvotes