BASIC MATHS
Basic Maths( yhi complete phyiscs ka base h good luck for your journey from satrting )
# Pythagoras theorem
$$ (P)^{2}+(B)^{2}=(H)^{2} $$
The following table:
SCT
PBP
HHB
- Sin $37^{\circ}\rightarrow3/5$
- Cos $37^{\circ}\rightarrow4/5$
- tan $37^{\circ}\rightarrow3/4$
- Sin $53^{\circ}\rightarrow4/5$
- Cos $53^{\circ}\rightarrow3/5$
- tan $53^{\circ}\rightarrow4/3$
# Conversion
Conversion from radian to degree ki Jagah 180°
- (i) $\frac{\pi}{2}rad\rightarrow\frac{3\times180}{2}=270^{\circ}$
- (ii) $\frac{4\pi}{3}rad\rightarrow\frac{4\times180}{3}=240^{\circ}$
# Conversion of degree into Radian !
- (i) $60^{\circ}\rightarrow60\times\frac{\pi}{180}=\frac{\pi}{3}rad$
- (ii) $90^{\circ}\rightarrow90\times\frac{\pi}{180}=\frac{\pi}{2}rad$
# Small angle approximation.
$$ \Rightarrow sin~\theta\approx\theta $$
$\frac{\pi}{180}$ Se Multiply kardo
(If $\theta$ is very small) toh radian
$\theta<5^{\circ}$ (Approx. Equal)
Equal toh $\theta=0^{\circ}$ Pe honge.
30° tak laga sakte
$\Rightarrow tan~\theta$ (If $\theta$ is very small) $\theta<10^{\circ}$
$\Rightarrow$ If $\theta$ is very small $(\theta<10^{\circ})$
$$ sin~\theta\approx tan~\theta\approx\theta $$
Trignometry Identities
- • $sin^{2}\theta+cos^{2}\theta=1$
- • $Sin(A+B)=Sin~A~cos~B+cos~A~sin~B$
- • $Sin(A-B)=Sin~A~cos~B-cos~A~Sin~B$
- • $cos(A+B)=cos~A~cos~B-sin~A~sin~B$
- • $cos(A-B)=cos~A~cos~B+sin~A~sin~B$
- • $tan(A+B)=\frac{tan~A+tan~B}{1-tan~A~tan~B}$
- • $tan(A-B)=\frac{tan~A-tan~B}{1+tan~A~tan~B}$
- • $1+tan^{2}\theta=sec^{2}\theta$
- • $1+cot^{2}\theta=cosec^{2}\theta$
- • $Sin~2~\theta=2~sin~\theta~cos~\theta$
- • $cos~2~\theta=cos^{2}\theta-sin^{2}\theta = 1-2~sin^{2}\theta = 2~cos^{2}\theta-1$
FOUR QUADRANT
# If $\theta$ is very small
$sin~\theta=\theta=tan~\theta$
$cos~\theta=\sqrt{1-\theta^{2}}$ (If $\theta$ is very small $cos~\theta \approx 1$)
- Sabse Pehle angle ko 180±, 360± me tod do.
- Quad Pata kar k +/- Lagao.
- (180±, 360±) bhul Jaao.
Agar humne $90^{\circ}$, $270^{\circ}$ me toda:
$sin \leftrightarrow cos$
$tan \leftrightarrow cot$
$Cosec \leftrightarrow Sec$
Example
- 1. $sin~150^{\circ}=sin(180-30)=+\frac{1}{2}$
- 2. $cos~210^{\circ}=cos(180+30)=-\frac{\sqrt{3}}{2}$
- 3. $sin~330^{\circ}=sin(360-30)=-\frac{1}{2}$
Asin $sin(360+\theta)=sin~\theta$
$cos(360+\theta)=cos~\theta$
$tan(360+\theta)=tan~\theta$
e.g. $sin~405^{\circ}=Sin(360+45) = +sin~45^{\circ} = \frac{1}{\sqrt{2}}$
$sin(-\theta)=-sin~\theta$
$cos(-\theta)=cos~\theta$
$tan(-\theta)=-tan~\theta$
$(sin~\theta)_{max}=+1$
$(sin~\theta)_{min}=-1$
$(cos~\theta)_{max}=+1$
$(cos~\theta)_{min}=-1$
$(sin^{2}\theta)_{max}=1$
$(sin^{2}\theta)_{min}=0$
$(cos^{2}\theta)_{max}=1$
$(cos^{2}\theta)_{min}=0$
$\rightarrow$ From $0^{\circ}$ to $90^{\circ}$
$\theta \uparrow = sin~\theta \uparrow$
$\theta \uparrow = tan~\theta \uparrow$
$\theta \uparrow = cos~\theta \downarrow$
Question
1. $y=2+3~sin~\theta$
$y_{max}=2+3\times1=5$
$y_{min}=2+3(-1)=-1$
3. $y=5+3tan~\theta$
$y_{max}=\infty$
$y_{min}=-\infty$
(i) $y=\frac{8}{5+3~sin~\theta}$
$y_{min}=\frac{8}{5+3}=1$
$y_{max}=\frac{8}{5-3}=4$
2. $y=3+4~cos\theta$
$y_{max}=3+4\times1=7$
$y_{min}=3-4=-1$
(ii) $y=\frac{10}{3+2~cos~\theta}$
$y_{max}=\frac{10}{3-2}=10$
$y_{min}=\frac{10}{3+2}=2$
# $y=a~sin~\theta+b~cos~\theta$
$y_{max}=\sqrt{a^{2}+b^{2}}$
$y_{min}=-\sqrt{a^{2}+b^{2}}$
Ques. $y=3~sin~\theta+4~cos~\theta$
$y_{max}=\sqrt{3^{2}+4^{2}}=5$
$y_{min}=-\sqrt{3^{2}+4^{2}}=-5$
Ques. Find value of $y_{max}$ and when $y=sin~3~\theta$
$y_{max}=1$
$3~\theta=90^{\circ} \implies \theta=30^{\circ}$
radian = 180 degree = 180x60 min = 180x60x60 sec
Ques CONVERT-
(i) 6 rad into min.
$\pi~rad=180~degree$
$\pi~rad=180\times60~min$
$1~rad=\frac{180\times60~min}{\pi}$
$6~rad=\frac{6\times10800~min}{\pi}$
(ii) 6 rad into second
$6~rad=\frac{6\times10800}{\pi}\times(60~sec)$
(iii) 6 degree into min
$1~degree=60~min$
$6~degree=6\times60~min=360~min$
(iv) 40 min into radian
$\pi~rad=180\times60~min$
$\pi~rad=10800~min$
$10800~min=\pi~rad$
$40~min=\frac{\pi}{10800}\times40~rad = \frac{\pi}{270}rad$
Ques. $\frac{sin~\theta+cos~\theta}{sin~\theta-cos~\theta}=\frac{9}{4}$. Find tan?
$\frac{sin~\theta}{cos~\theta}=\frac{9+4}{9-4}=\frac{13}{5}=tan~\theta$
# Distance between two point
2D: $A(x_{1}, y_{1})$ & $B(x_{2}, y_{2})$
$$ AB=\sqrt{(x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2}} $$
3D: $A(x_{1}, y_{1}, z_{1})$ & $B(x_{2}, y_{2}, z_{2})$
$$ AB=\sqrt{(x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2}+(z_{2}-z_{1})^{2}} $$
Mid Point = $(\frac{x_{1}+x_{2}}{2},\frac{y_{1}+y_{2}}{2})$
Distance of 'P' $(x,y,z)$ from origin:
$OA=\sqrt{x^{2}+y^{2}}$
$OA=\sqrt{x^{2}+y^{2}+z^{2}}$
Qus.
A(7,3), B(10,7)
$AB=\sqrt{(10-7)^{2}+(7-3)^{2}} = 5$
A(2,3,4), B(5,7,9)
$AB=\sqrt{(5-2)^{2}+(7-3)^{2}+(9-4)^{2}} = 5\sqrt{2}$
A(4,6), B(10,12). Mid Point C?
$C=(\frac{4+10}{2},\frac{6+12}{2}) = (7,9)$
# Slope of Straight Line (Continued)
Equation of straight line
$$ y=mx+c $$
$m=slope$
$At~x=0$, $y=0+c \implies c = y$ intercept / $x=0$ Par 'y' ki value.
Slope of line joining A $(x_1, y_1)$ to B $(x_2, y_2)$:
$$ Slope=tan~\theta=\frac{y_{2}-y_{1}}{x_{2}-x_{1}} $$
Ques. $y=\sqrt{3}x+10$
$m=\sqrt{3}=slope=tan~\theta \therefore \theta=60^{\circ}$
At $x=0$, $y=10 \implies c=10$
Ques. $y=\frac{x}{\sqrt{3}}+5$
$m=\frac{1}{\sqrt{3}}=tan~\theta \therefore \theta=30^{\circ}$
At $x=0$, $y=5$ or $c=5$
Qus. $y=x-10$
$m=1=tan~\theta=45^{\circ}$
Comparing Slopes
$\theta_{3} > \theta_{2} > \theta_{1}$
$tan~\theta_{3} > tan~\theta_{2} > tan~\theta_{1}$
$(Slope)_{3} > (Slope)_{2} > (Slope)_{1}$
More Equation Examples
# $3x+4y+5=0$
$4y=-3x-5 \implies y=-\frac{3}{4}x-\frac{5}{4}$
$Slope=-\frac{3}{4}$, $C=\frac{-5}{4}$
Ques. Find equation passing through (2,3) having slope +10.
$y=mx+c \implies 3=10(2)+c \implies C=-17$
$y=10x-17$
To Find equation if two points are given: (2,3) and (4,5)
$Slope = \frac{5-3}{4-2} = 1 = m$
$y=x+c \implies 3=2+c \implies c=1$
$\therefore y=x+1$
# Graphs & Curves
$y=x^{2}$
$y^{2}=x$
$y=-x^{2}$
$y^{2}=-x$
# $xy=c$ (e.g. $xy=4$) $\implies$ Rectangular Hyperbola
# Geometric Progression
General Form: $a, ar, ar^{2}, ar^{3}$
First term = $a$, $r$ = common ratio
$$ S_{\infty}=\frac{a}{1-r} $$ (For $|r| < 1$)
Ques. Find $1+\frac{1}{4}+\frac{1}{16}+\frac{1}{32}+....\infty$
$a=1$, $r=\frac{1}{4}$ $\implies S_{\infty}=\frac{1}{1-\frac{1}{4}}=\frac{4}{3}$
# Thermodynamics Graphs ($PV=nRT$)
V vs T Graph (At constant Pressure)
$V = (\frac{nR}{P})T \implies y=mx$
$tan~\theta = \frac{nR}{P}$
P vs V Graph (Isotherms)
# Photoelectric Effect Graphs
$E=\Phi+(KE)_{max} \implies hv=\Phi+eV_{0}$
$V_{0} = (\frac{h}{e})v - \frac{\Phi}{e}$
Comparing with $y=mx-c \implies Slope = \frac{h}{e}$
# Quadratic Equation
$$ ax^{2}+bx+c=0 $$
$b^{2}>4ac$ (two real roots)
$$ x=\frac{-b\pm\sqrt{b^{2}-4ac}}{2a} $$
Ques. $x^{2}-6x+5=0$
$a=1, b=-6, c=5$
$x_{1}=\frac{-(-6)+\sqrt{36-4(1)(5)}}{2(1)} = \frac{6+4}{2} = 5$
$x_{2}=\frac{-(-6)-\sqrt{36-20}}{2} = \frac{6-4}{2} = 1$
# DIFFERENTIATION (Start)
$$ y=x^{n} \implies \frac{dy}{dx}=nx^{n-1} $$
- $sin~x\rightarrow cos~x$
- $cos~x\rightarrow -sin~x$
- $tan~x\rightarrow sec^{2}x$
- $e^{x}\rightarrow e^{x}$
- Constant $\rightarrow 0$
- $ln~x\rightarrow\frac{1}{x}$
- $cot~x\rightarrow -cosec^{2}x$
# Differentiation (Examples)
Tangent at a Point
Ques. $y=x^{2}$. Find $\frac{dy}{dx}$ at $x=\frac{1}{2}$
$\frac{dy}{dx}=2x \implies 2(\frac{1}{2})=1$
$\frac{dy}{dx}=1=slope=tan~\theta \implies \theta=45^{\circ}$
PRODUCT RULE
$y=u\cdot v \implies \frac{dy}{dx}=u\cdot\frac{dv}{dx}+v\cdot\frac{du}{dx}$
Q. $y=x^{2}\sin x \implies \frac{dy}{dx}=x^{2}\cdot\cos x + \sin x\cdot(2x)$
QUOTIENT RULE
$y=\frac{u}{v} \implies \frac{dy}{dx}=\frac{v\frac{du}{dx}-u\frac{dv}{dx}}{v^{2}}$
Q. $y=\frac{x^{2}}{\sin x} \implies \frac{dy}{dx}=\frac{(\sin x)(2x)-x^{2}\cos x}{(\sin x)^{2}}$
# Double Differentiation
1. $y=x^{3}+\sin x \implies y'=3x^{2}+\cos x \implies y''=6x-\sin x$
2. $y=x^{5}+e^{x}+\sin x \implies y'=5x^{4}+e^{x}+\cos x \implies y''=20x^{3}+e^{x}-\sin x$
# Chain Rule & Geometrical Meaning
1. $y=\sin(x^{3}) \implies \frac{dy}{dx}=\cos(x^{3})\times 3x^{2}$
2. $y=ln(\sin(x^{2}+2)) \implies y'=\frac{1}{\sin(x^{2}+2)}\times\cos(x^{2}+2)\times(2x)$
3. $y=A\sin(\omega t+\phi) \implies \frac{dy}{dt}=A\omega\cos(\omega t+\phi)$
kisi bhi curve k kisi bhi point Par dy/dx ka matlab hai us point Par tangent ka slope.
$\frac{dy}{dx}$ at A = slope of tangent at A = $\tan 60^{\circ} = \sqrt{3}$
Binomial Expansion
If $x \ll 1$
$$ (1+x)^{n} \approx 1+nx $$
1. $(1.001)^{3} = (1+.001)^{3} = 1+3\times(.001) = 1.003$
Exponential Decay Graph
$y=e^{-x}$ (for $x \ge 0$)
# Maxima & Minima
Q. $y=x^{3}-3x^{2}+6x$, Find $y_{min}$ & $y_{max}$
$\frac{dy}{dx}=3x^{2}-6x=0 \implies 3x(x-2)=0 \implies x=0, 2$
$\frac{d^{2}y}{dx^{2}}=6x-6$
At $x=0 \rightarrow 6(0)-6=-6$ (Negative, Maxima). $y_{max}=0-0+0=6$
At $x=2 \rightarrow 6(2)-6=6$ (Positive, Minima). $y_{min}=2^{3}-3(2)^{2}+6(2)=2$
# Integration
- $\int x^{n}dx=\frac{x^{n+1}}{n+1}+c$
- $\int\frac{1}{x}dx=ln~x+c$
- $\int e^{x}dx=e^{x}+c$
- $\int\cos x~dx=\sin x+c$
- $\int\sin x~dx=-\cos x+c$
- $\int\sec^{2}x~dx=\tan x+c$
Definite Integral
1. $\int_{2}^{4}xdx=[\frac{x^{2}}{2}]_{2}^{4}=[\frac{16}{2}-\frac{4}{2}]=8-2=6$
2. $\int_{0}^{\pi}\sin\theta~d\theta=[-\cos\theta]_{0}^{\pi}=-(\cos\pi-\cos 0^{\circ})=-(-1-1)=2$
Substitution Form
$\int\sin(ax+b)dx=\frac{-\cos(ax+b)}{a}+c$
$\int e^{ax+b}dx=\frac{e^{ax+b}}{a}+c$
Trigonometry Table
| $\theta$ | 0° | 30° | 45° | 60° | 90° | 120° | 135° | 150° | 180° |
|---|---|---|---|---|---|---|---|---|---|
| Sin | 0 | 1/2 | $1/\sqrt{2}$ | $\sqrt{3}/2$ | 1 | $\sqrt{3}/2$ | $1/\sqrt{2}$ | 1/2 | 0 |
| Cos | 1 | $\sqrt{3}/2$ | $1/\sqrt{2}$ | 1/2 | 0 | -1/2 | $-1/\sqrt{2}$ | $-\sqrt{3}/2$ | -1 |
| Tan | 0 | $1/\sqrt{3}$ | 1 | $\sqrt{3}$ | $\infty$ | $-\sqrt{3}$ | -1 | $-1/\sqrt{3}$ | 0 |
Sinx Graph (Integration Area)
$\int_{0}^{\pi/2}\sin x~dx=1$ | $\int_{0}^{\pi}\sin x~dx=2$
Cosx Graph (Integration Area)
$\int_{0}^{\pi}\cos x~dx=1-1=0$
Integration of $\sin^{2}x$ & $\cos^{2}x$
Formula used: $\cos 2x=1-2\sin^{2}x \implies \sin^{2}x=\frac{1}{2}(1-\cos 2x)$
$\int\sin^{2}xdx=\int\frac{1}{2}(1-\cos 2x)dx = \frac{x}{2}-\frac{\sin 2x}{4}+c$
$\int\cos^{2}xdx=\int\frac{1}{2}(1+\cos 2x)dx = \frac{x}{2}+\frac{\sin 2x}{4}+c$
# LOGARITHM
$log_{b}a=c \implies a=b^{c}$
Natural log $(ln)$: $ln~x=y \implies log_{e}x=y \implies x=e^{y}$
Example: $log_{2}8=3 \implies 2^{3}=8$
$log_{a}a=1$ | $ln~e=1$ | $log_{10}10=1$
1. $log~m+log~n=log(m\cdot n)$
2. $log(\frac{m}{n})=log~m-log~n$
3. $log_{b}a^{n}=n~log_{b}a$
Q. $log~8-log~4+log~2 = log(\frac{8}{4}\times 2)=log~4$
Q. $log_{5}125=log_{5}5^{3}=3~log_{5}5=3$
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