Sin, cos, Tan who knows what they mean No class!

Sin, cos, Tan who knows what they mean No class!

The opposite side of sin sine direct triangle is bigger than the hypotenuse
In COS cosine right triangle, the adjacent edge is smaller than the hypotenuse
Tan tangent opposite edge than adjacent edge
1. Induction formula
sin(-a)=-sin(a)
cos(-a)=cos(a)
sin(π2-a)=cos(a)
cos(π2-a)=sin(a)
sin(π2+a)=cos(a)
cos(π2+a)=-sin(a)
sin(π-a)=sin(a)
cos(π-a)=-cos(a)
sin(π+a)=-sin(a)
cos(π+a)=-cos(a)
2. Trigonometric function of sum and difference of two angles
sin(a+b)=sin(a)cos(b)+cos(α)sin(b)
cos(a+b)=cos(a)cos(b)-sin(a)sin(b)
sin(a-b)=sin(a)cos(b)-cos(a)sin(b)
cos(a-b)=cos(a)cos(b)+sin(a)sin(b)
tan(a+b)=tan(a)+tan(b)1-tan(a)tan(b)
tan(a-b)=tan(a)-tan(b)1+tan(a)tan(b)
3. Sum difference product formula
sin(a)+sin(b)=2sin(a+b2)cos(a-b2)
sin(a)−sin(b)=2cos(a+b2)sin(a-b2)
cos(a)+cos(b)=2cos(a+b2)cos(a-b2)
cos(a)-cos(b)=-2sin(a+b2)sin(a-b2)
4. Double angle formula
sin(2a)=2sin(a)cos(b)
cos(2a)=cos2(a)-sin2(a)=2cos2(a)-1=1-2sin2(a)
5. Half angle formula
sin2(a2)=1-cos(a)2
cos2(a2)=1+cos(a)2
tan(a2)=1-cos(a)sin(a)=sina1+cos(a)
6. Universal formula
sin(a)=2tan(a2)1+tan2(a2)
cos(a)=1-tan2(a2)1+tan2(a2)
tan(a)=2tan(a2)1-tan2(a2)
7. Other formulas (derived)
A &; sin (a) + B &; cos (a) = A2 + b2sin (a + C) where Tan & copy; = Ba
A &; sin (a) + B &; cos (a) = A2 + b2cos (A-C) where Tan & copy; = ab
1+sin(a)=(sin(a2)+cos(a2))2
1-sin(a)=(sin(a2)-cos(a2))2

The side view of a cylinder is a square whose height is several times the diameter of its bottom

It's PI times

Xiaohua knows that the light spot under the shade of trees is the image of the sun on the ground through the small holes between the leaves. He measured that the diameter of the light spot is 7.0cm, and the distance between the light spot and the small hole is 7.5m. He also found that the distance between the sun and the earth is 15000000000 m from the book, so he can estimate the diameter of the sun is

150000000000/7.5=20000000000
The diameter of the sun is 2000000000 * 0.07 = 1400000000m

What should be paid attention to in high school physics functional principle
The knowledge involved in the formula of functional principle

High school physics to the end of all knowledge points will be integrated, the gravity field, magnetic field field with coordination, force analysis is very important. Functional principle is not the key, do a simple topic focus on review! Mechanical energy balance and other quantities of the relationship between clear, set the formula can generally get a higher score!

The perimeter of the rectangle is 30cm, and the length is 2cm more than the width. Calculate the area of the rectangle
Wrong, the circumference of the rectangle is 36cm, and the length is 2cm more than the width. Calculate the area of the rectangle

36/2=18
(18+2)/2=10
18-10=8
10*8=80

The law () can be used to simplify the calculation

The law of combination of multiplication can be used to simplify the calculation

Given that the function f (x) = 1 / (x-1 of 2) + A is an odd function, find the value of a and the range of function

f(x)= 1/(2^x-1)+ A
f(-x)
= 1/[2^(-x)-1]+ A
= 2^x/(1-2^x)+ A
According to the meaning of the title:
f(-x)= -f(x)
Namely:
2^x/(1-2^x)+ A = -1/(2^x-1)- A
Or:
2A= -1/(2^x-1)- 2^x/(1-2^x)= 1
So: a = 1 / 2
Original function = 1 / (2 ^ x-1) + 1 / 2
Range (1 / 2, positive infinity)

There are two identical rectangles, 8 cm in length and 3 cm in width. If they are stacked together as shown in the figure, what is the perimeter of the figure?

(8 + 3) × 2 × 2-3 × 4, = 11 × 2 × 2-3 × 4, = 44-12, = 32 (CM); a: the circumference of this figure is 32 cm

3, 3, 8, 8, how do you calculate with 24 o'clock

8 / (3-8 / 3) = 24, that's it

Given that the recurrence formula of sequence {an} is: A1 = 1, an + 1 = an / 2An + 1, n belongs to positive integer, then the general term formula of sequence {an} is

You don't have parentheses. I guess
a(n+1)=an/(2an+1)
1/a(n+1)=(2an+1)/an=2+1/an
So the sequence {1 / an} is an arithmetic sequence with 1 as the first term and 2 as the tolerance
So 1 / an = 1 + (n-1) 2 = 2N-1
an=1/(2n-1)