## Trigonometric function (11 13:35:32) If 0 ＜ a ＜ 90 degrees, and the 10 times of a is the same as the final edge of a, find a

Because 10A = a + 360 * k

So 9A = 360K

a=40k

Because 0

### Trigonometric function (3:23:5:35) What is the definition field of function y = ㏒ 10 [sin (cosx)]?

For a logarithmic function to be meaningful, the value in brackets must be greater than 0

That is, sin (cosx) > 0. If the sine function is greater than 0, the value ∈ (2k π, π + 2K π), (k = 0, ± 1, ± 2...) in parentheses is required. Considering that the value range of cosx is [- 1,1], there must be k = 0. That is, the value ∈ (0, π) in parentheses and π > 1. Therefore, when the value range of cosx ∈ (0,1], X is the definition domain of Y

Therefore, X ∈ (- π / 2 + 2K π, π / 2 + 2K π)

### Trigonometric function (22 12:26:25) Known sin α= 2cos α Requirements: ①(sin α- 4cos α)/ (5sin α+ 2cos α) ②sin2 α+ 2sin α cos α Value of

sin α= 2cos α , tana=2

①(sin α- 4cos α)/ (5sin α+ 2cos α)

=(tana-4)/(5tana+2)

=-1/6

sin^2 α+ 2sin α cos α

=(sin^2 α+ 2sin α cos α)/ (sin^2a+cos^2a)

=(tan^2a+2tana)/(tan^2a+1)

=8/5

### Trigonometric function (11 16:41:22) Given 2sina = cosa, find the value of 2sin2a + 3sinacosa-cos2a

2sin2a+3sinacosa-cos2a

= 4sinacosa+3sinacosa-(cosa2-sina2)

=sina2-cosa2+7sinacosa

Because 2sina = cosa

So the original formula is = sina2-4sina2 + 7sina * 2sina

=11sina2

### In isosceles triangle, the degree longitude of top angle and bottom angle is 2:3, the top angle is () degrees and the bottom angle is () degrees

Because it's isosceles, the base angles are equal

That is, 2:3:3

If the top angle is 2x degrees, the bottom angle is 3x degrees

2X+3X+3X=180

X=22.5

The top angle is 45 degrees and the bottom angle is 67.5 degrees

### Answers to page 58 of mathematics classroom assignment book in Volume 2 of grade 6

9. There are 6 combinations for summation: 3 + 4 = 7, 3 + 5 = 8, 3 + 6 = 9, 4 + 5 = 9, 4 + 6 = 10, 5 + 6 = 11. There are 4 kinds of sums that are singular, accounting for 4 / 6 = 2 / 3, and 2 kinds of sums that are even, accounting for 2 / 6 = 1 / 3. Because 2 / 3 > 1 / 3, it is more likely to win if they are singular

There are six combinations of quadrature: 3 × 4=12、3 × 5=15、3 × 6=18、4 × 5=20、4 × 6=24、5 × 6 = 30, one product is singular, accounting for 1 / 6, and five products are even, accounting for 5 / 6. Because 1 / 6